Haptic keyboard system

ABSTRACT

One variation of a keyboard system includes: a substrate including an array of inductors; a tactile layer arranged over the substrate defining an array of key locations over the array of inductors; an array of magnetic elements, each arranged within the tactile layer at a key location configured to inductively couple to an adjacent inductor and configured to move relative to the adjacent inductor responsive to application of a force on the tactile layer at the key location; and a controller configured to read electrical values from the inductors. In response to detecting a change in electrical value at a first inductor, the controller also configured to: register a first keystroke of a first key type associated with a first key location defined over the first inductor; and drive an oscillating voltage across the first inductor to oscillate the tactile layer over the substrate during a haptic feedback cycle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 371 to InternationalApplication No. PCT/US21/53660, filed on 5 Oct. 2021, which claimspriority to U.S. Provisional Patent Application 63/088,359, filed on 6Oct. 2020, each of which is incorporated in its entirety by thisreference.

This application is related to U.S. patent application Ser. No.17/367,572, filed on 5 Jul. 2021, which is incorporated in its entiretyby this reference.

TECHNICAL FIELD

This invention relates generally to the field of user input devices andmore specifically to a new and useful keyboard system with key-levelhaptic feedback in the field of user input devices.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of a keyboard system;

FIG. 2 is a schematic representation of one variation of the keyboardsystem;

FIG. 3 is a schematic representation of one variation of the keyboardsystem;

FIG. 4 is a schematic representation of one variation of the keyboardsystem;

FIG. 5 is a schematic representation of one variation of the keyboardsystem;

FIG. 6 is a schematic representation of one variation of the keyboardsystem;

FIG. 7 is a schematic representation of one variation of the keyboardsystem;

FIG. 8 is a schematic representation of one variation of the keyboardsystem;

FIG. 9 is a flowchart representation of one variation of the keyboardsystem;

FIG. 10 is a flowchart representation of one variation of the keyboardsystem; and

FIG. 11 is a schematic representation of one variation of the keyboardsystem.

DESCRIPTION OF THE EMBODIMENTS

The following description of embodiments of the invention is notintended to limit the invention to these embodiments but rather toenable a person skilled in the art to make and use this invention.Variations, configurations, implementations, example implementations,and examples described herein are optional and are not exclusive to thevariations, configurations, implementations, example implementations,and examples they describe. The invention described herein can includeany and all permutations of these variations, configurations,implementations, example implementations, and examples.

1. Keyboard System

As shown in FIGS. 1-4 , a keyboard system 100 includes: a substrate 110;a force-sensitive layer 160; a set of keys; a set of coil drivers 171;and a controller 170. The substrate 110 includes: a substrate 110; anarray of drive electrode and sense electrode pairs 112 arranged across atop layer 115 of the substrate 110 at a set of key locations 132; a setof multi-layer inductors 120 arranged across multiple layers of thesubstrate 110 at each key location 132 in the set of key locations 132;and an inductor control circuit electrically coupling the set ofmulti-layer inductors 120 to the set of coil drivers 171. The set ofcoil drivers 171 are configured to selectively polarize individualmulti-layer inductors 120 in the set of multi-layer inductors 120. Theforce-sensitive layer 160 is arranged over the substrate 110 adjacentthe array of drive electrode and sense electrode pairs 112 and exhibitsbulk change in local resistance as a function of applied force. The setof keys are arranged over the force-sensitive layer 160. Each key in theset of keys: is arranged over the force-sensitive layer 160 in a keylocation 132, in the set of key locations 132, over an multi-layerinductor 120 in the set of multi-layer inductors 120; includes a body;and includes a magnetic element 150 configured to magnetically couple tothe multi-layer inductor 120 and to oscillate the body of the keyresponsive to polarization of the multi-layer inductor 120.

The controller 170 is configured: to detect an input on a particular keyin the set of keys responsive to a change in electrical value between aparticular drive electrode and sense electrode pair 112 in the array ofdrive electrode and sense electrode pairs 112; and to trigger a coildriver 171, in the set of coil drivers 171, to polarize a particularmulti-layer inductor 120 proximal the particular key in response to theinput.

One variation of the keyboard system 100 incudes: a substrate 110; atactile layer 130; a force-sensitive layer 160; an array of magneticelements 150; and a controller 170. The substrate 110 includes: an arrayof electrodes; and an array of inductors 120 arranged below the array ofelectrodes. The tactile layer 130: is arranged over the substrate 110;and defines an array of key locations 132 over the array of inductors120. The force-sensitive layer 160 is interposed between the tactilelayer 130 and the substrate and exhibits variations in local contactresistance across the array of electrodes responsive to variations inforce applied to the tactile layer 130 at the array of key locations132. Each magnetic element 150 in the array of magnetic elements 150: isarranged within the tactile layer 130 at a key location 132 in the arrayof key locations 132; and is configured to inductively couple to anadjacent inductor 120 in the array of inductors 120. The controller 170is configured to read electrical values from the array of electrodes.The controller 170 is also configured to, at a first time and inresponse to detecting a change in electrical value at a first senseelectrode, in the array of electrodes: register a first keystroke of afirst key type associated with a first key location 132, in the array ofkey locations 132, defined over the first sense electrode; and drive anoscillating voltage across a first inductor 120, arranged below thefirst sense electrode, during a first haptic feedback cycle to a) inducealternating magnetic coupling between the first inductor 120 and a firstmagnetic element 150, in the array of magnetic elements 150, arrangedwithin the tactile layer 130 at the first key location 132 and b)oscillate the tactile layer 130, at the first key location 132, relativeto the substrate 110.

2. Applications

Generally, the keyboard system 100 functions as a computer keyboard (orkeypad, or other typewriter-style device) including anindependently-operated, non-mechanical haptic subsystem integrated intoeach individual key and configured to emulate mechanical “snap” buttonswithout sliding or rotating components and with minimal motion (e.g.,100 microns rather more than one millimeter).

In particular, the keyboard system 100 includes a single substrate 110that contains: an array of drive electrode and sense electrode pairs 112that cooperate with the force-sensitive layer 160 to form a touch sensorat each key location 132 of a keyboard layout; a set of multi-layerinductors 120 patterned across multiple layers of the substrate110—below the touch sensor—at each key location 132; an inductor controlcircuit patterned across the substrate 110 and configured to distributealternating current signals to individual inductors 120; and a set ofcoil drivers 171 connected to the set of inductors 120 via the inductorcontrol circuit and configured to energize individual inductors 120 viathe inductor control circuit.

The force-sensitive layer 160 is arranged over the substrate 110adjacent the touch sensor electrode array and exhibits bulk change inlocal resistance as a function of applied pressure such that applicationof a force yields a measurable change in electrical value (e.g.,resistance) across an adjacent cluster of drive electrode and senseelectrode pairs 112 in the force sensor.

The set of keys is arranged across the force-sensitive layer 160,including one key located at each key location 132 and including amagnetic element 150 (e.g., a cylindrical magnet, an annular magnet, aHalbach array) configured to magnetically couple to the adjacentinductor 120 and thus oscillate the key relative to the substrate 110when the adjacent inductor 120 is energized.

During a scan cycle, the controller 170 can: read a resistance valuefrom each drive electrode and sense electrode pair 112; interpretmagnitudes forces (or pressures) applied to each drive electrode andsense electrode pair 112—via the set of keys and the force-sensitivelayer 160—as a function of (e.g., inversely proportional to) resistancevalues read from these drive electrode and sense electrode pairs 112;store these forces in a force image containing an array of pixelsrepresenting force magnitudes interpreted at corresponding driveelectrode and sense electrode pairs 112; detect a contiguous cluster ofpixels in the force image exhibiting force magnitudes greater than abaseline force and/or contained within a boundary of a single key in thekeyboard layout; and calculate a total force magnitude applied acrossthis cluster of pixels. Then, if this total force magnitude appliedacross this cluster of pixels exceeds a threshold force (e.g., 160grams), the controller 170 can: confirm a keystroke input at aparticular key located over a cluster of drive electrode and senseelectrode pairs 112 represented by the cluster of pixels in the forceimage; identify an inductor 120 address of an inductor 120 located belowthis particular key; identify and output a keystroke value (e.g., “a,”“SHIFT”) associated with this particular key; and trigger a coil driver171 to output an alternating current to the inductor 120 address,thereby inducing magnetic coupling between the inductor 120 at theinductor 120 address and the magnetic element 150 in the particular key,oscillating the particular key during a “haptic feedback cycle,” andemulating mechanical actuation of a mechanical key of a keyboard—such aswithin a 50-millisecond scan cycle.

The controller 170 can implement similar methods and techniques todetect concurrent keystroke inputs at multiple different keys (e.g., at“SHIFT” and “a” keys) during one scan cycle and can trigger the set ofcoil drivers 171 to selectively polarize inductors 120 at key locations132 cospatial with these detected inputs, thereby individually andindependently vibrating each of these keys to emulate concurrentmechanical actuation of these keys.

Therefore, the keyboard system 100 can enable independently-operablehaptic feedback at each individual key within a keyboard layout withoutmoving (i.e., rotating, sliding) components, thereby enabling thekeyboard system 100 to include smaller, thinner, and/or lightercomponents without sacrificing durability and operating life.Furthermore, the keyboard system 100 can include a total quantity ofdiscrete components that approaches the total quantity of keys in thekeyboard layout—rather than multiples of this quantity of keys—therebyreducing cost, complexity, and failure modes for the keyboard system100. For example, the keyboard system 100 can include: a substrate 110that includes a touch sensor electrode array, multi-layer inductors 120for key-specific haptic feedback, an inductor control circuit, and coildrivers 171 in one singular assembly; a force-sensitive layer 160 thatcooperates with the touch sensor electrode array to form apressure-sensitive touch sensor; and one key at each key location 132 inthe keyboard layout.

Furthermore, by locating all electrical components within one substrate110 assembly below the force-sensitive layer 160 and eliminatingmechanical actuation of keys, the keyboard system 100 can eliminate athick frame around each key and thus enable each key to extend up to(e.g., within 50 microns) of the adjacent keys, thereby forming a nearlycontinuous keyboard surface and reducing or eliminating opportunity fordirt or other particulate to foul haptic operation of these key.

The keyboard system 100 is described herein as a keyboard (e.g., aQWERTY keyboard) integrated into a laptop computer or desktop keyboardperipheral. However, the keyboard system 100 can additionally oralternatively form a keypad or other button interface exhibitingkey-specific haptic feedback that emulates tactile perception ofmechanical “snap” buttons without moving mechanical components.

Generally, the system 100 is described herein as including an array ofkeys, each including a set of (i.e., one or more) magnetic elements thatinterface with one inductor to oscillate the key responsive todepression of the key. However, a key (e.g., a “spacebar”) within thesystem 100 can be arranged over multiple discrete inductors and caninclude multiple sets of laterally-offset magnetic elements, eachconfigured to interface with one inductor to (predominately) oscillateone region of the key, such as responsive to local depression of acorresponding region of the key or in response to an input that triggersthe computing device to execute an action associated with thecorresponding region of the key.

3. Independent Key Haptics

Generally, a magnetic element 150 integrated within a key and aninductor 120 integrated into the substrate 110 at a key location 132below this key can cooperate to form a vibrator configured to oscillatethe key relative to the substrate 110.

3.1 Inductor

In particular, the inductor 120 can be formed by a set of planar coiltraces etched or fabricated on each of multiple structural layers of thesubstrate 110 and interconnected by vias through these layers to formone continuous coil with multiple (e.g., many) turns below the magneticelement 150 integrated into the adjacent key.

For example, the inductor 120 can include: a first multi-loop tracespiraling inward in a first wind direction on a first, bottom layer ofthe substrate 110; a second multi-loop trace spiraling outward in thefirst wind direction on a second layer 117 of the substrate 110; a thirdmulti-loop trace spiraling inward in the first wind direction on a thirdlayer 118 of the substrate 110; and a fourth multi-loop trace spiralingoutward in the first wind direction—between adjacent loops of the secondtrace—on the second layer 117 of the substrate 110. Vias can connect:the end of the first spiral trace in the first layer 116 to the start ofthe second spiral trace in the second layer 117; the end of the secondspiral trace in the second layer 117 to the start of the third spiraltrace in the third layer 118; the end of the third spiral trace in thethird layer 118 to the start of the fourth spiral trace in the secondlayer 117; and the end of the fourth spiral trace in the second layer117 to the first, bottom layer near the start of the first spiral trace.

Thus, in this example, an inductor 120 can include multiple sets ofspiral traces spanning multiple layers of the substrate 110 andconnected to form a continuous, multi-loop coil with terminals of theinductor 120 falling in close proximity (e.g., within two millimeters)on the first, bottom layer of the substrate 110.

3.2 Magnetic Element

The key can include a magnetic element 150 overmolded, bonded, orotherwise integrated into a body of the key (e.g., a molded siliconebody) and can be arranged over the inductor 120 with the magneticelement 150 centered over the inductor 120. The controller 170 cantherefore trigger a coil driver 171 to supply an alternating current tothe inductor 120—such as via the inductor control circuit coupled to theinductor 120 and integrated into the substrate 110—in order to induce analternating magnetic field from the inductor 120 perpendicular to thetouch sensor surface, thereby generating alternating magnetic couplingbetween the magnetic element 150 and the inductor 120 and thusoscillating the key relative to the substrate 110, which a user touchingthe key with her finger may tactilely perceive and interpret asmechanical depression of the key.

3.2 Other Key and Inductor Pairs

The keyboard system 100 can include additional pairs of: inductors 120integrated into the substrate 110; and adjacent keys with integratedmagnetic elements 150 to form a keyboard (or keypad, etc.) withdiscrete, independently-actuated haptic controls at each individual key.

4. Substrate

Generally, the substrate 110 includes a set of non-conductive structurallayers interposed between a set of conductive layers patterned (e.g.,etched) to form: an array of drive electrode and sense electrode pairs112 of a touch sensor; a multi-layer inductive coil (hereinafter an“inductor 120”) below each key location 132 of the keyboard (or keypad,etc.); and an inductor control circuit connected to the set ofmulti-layer inductive coils. The substrate 110 also locates (or isconnected to): a set of coil drivers 171 configured to selectivelyoutput alternating current to individual inductors 120; and/or thecontroller 170. For example, the substrate 110 can include a multi-layerprinted circuit board (or “PCB”) that includes—under each key location132 of the keyboard—one drive electrode and sense electrode pair 112fabricated on a top layer 115 of the substrate 110 and one inductor 120fabricated from alternating spiral traces connected by vias in multiplelayers of substrate 110.

In particular, the drive electrode and sense electrode pairs 112,multi-layer inductors 120, and inductor control circuits (and lightingelements, etc.) can be fabricated across a single, multi-layer substrate110 that both structurally supports the force-sensitive layer 160 andkeys above, connects the array of drive electrode and sense electrodepairs 112 to the controller 170 for sampling and input detection, anddistributes power to individual multi-layer inductors 120 during hapticfeedback cycles. For example, the substrate 110 can be fabricated viamulti-layer substrate 110 fabrication techniques; and the controller 170coil drivers 171, integrated circuits, light elements 180, power anddata connectors, and other circuit components can be soldered directlyto the substrate 110 to complete all electronic and control assembly ofthe keyboard system 100 within this single substrate 110 assembly.

4.1 Drive and Sense Electrode Pairs

The array of sense electrode and drive electrode pairs are patternedacross a top conductive layer of the substrate 110. For example, and asdescribed in U.S. patent application Ser. No. 14/499,001, the substrate110 can include a grid of inter-digitated drive electrodes and senseelectrodes patterned across its top conductive layer. In this example,rows of drive electrodes connected in series and columns of senseelectrodes connected in series can be patterned across the topconductive layer of the substrate 110 to form an array of driveelectrode and sense electrode pairs 112.

The force-sensitive layer 160 is arranged over the substrate 110 andspans gaps between each drive electrode and sense electrode pair 112such that, when a key is depressed, a local force is carried from thekey into the force-sensitive layer 160, which locally compresses theforce-sensitive layer 160, decreases the local resistance of theforce-sensitive layer 160 below the key, and decreases the resistanceacross adjacent drive electrode and sense electrode pairs 112 on thesubstrate 110. In particular, the resistance across these adjacent driveelectrode and sense electrode pairs 112 may vary (e.g., drop)proportional (e.g., as a linear, inverse, or quadratic function) to themagnitude of the force applied to the key.

As described below, the controller 170 160 can read resistance valuesacross each drive electrode and sense electrode pair 112 and caninterpret position and force magnitudes of inputs across the set of keysbased on resistance values read from these drive electrode and senseelectrode pairs 112.

4.2 Inductor

In one implementation shown in FIGS. 1-4 , the keyboard system 100includes a multi-layer substrate 110 that includes: a set of (e.g., six)conductive layers etched to form a suite of conductive traces; and a setof (e.g., five) structural layers interposed between the set ofconductive layers. In this implementation, the substrate 110 includes aset of overlapping, interconnected spiral traces fabricated on a set ofadjacent layers of the substrate 110 to form a single, multi-turn,multi-layer inductor 120 (that exhibits greater inductance and thereforegreater magnetic coupling to an adjacent magnetic element 150 than asingle spiral trace) at each key location 132. The spiral traces withinone inductor 120 can be coaxially aligned about a common vertical axis(e.g., centered below the adjacent key and magnetic element 150) andelectrically interconnected by a set of vias passing through theintervening structural layers of the substrate 110.

In one example in which each inductor 120 spans an odd number of (e.g.,3, 5) conductive layers of the substrate 110, the center conductivelayers of this set of conductive layers can include pairs of concentricand offset spiral traces that both define starts on the outside of thesespiral traces and ends near the center of these spiral traces (or viceversa) such that the end of the last spiral trace (i.e., a “secondterminal”) in the conductive layer “2” of the substrate 110 terminatesnear an outside of this last spiral trace—and near the start of thefirst spiral trace (i.e., a “first terminal) on the adjacent conductivelayer “1” of the substrate 110. In this example, in a substrate 110 thatincludes a three-layer inductor 120, conductive layer “2” of thesubstrate 110 can include two concentric and offset spiral traces.Alternatively, in a substrate 110 that includes a five-layer inductor120, conductive layers “2,” “3,” and “4” of the substrate 110 caninclude two concentric and offset spiral traces.

Furthermore, conductive layers in the substrate 110 can exhibitdifferent thicknesses. Accordingly, spiral traces fabricated on thickerconductive layers may exhibit narrow trace widths, and spiral tracesfabricated on thinner conductive layers may exhibit wider trace widthsin order to achieve similar electrical resistance across these spiraltraces. Similarly, the lower conductive layers of the substrate 110 caninclude thicker (or “heavier”) layers of conductive material (e.g.,one-ounce copper approximately 35 microns in thickness) in order toaccommodate narrow trace widths and more turns per unit area of spiraltraces in these conductive layers, thereby increasing inductance of thespiral trace and increasing magnetic coupling of the inductor 120 to anadjacent magnetic element 150 during a haptic feedback cycle.Conversely, upper layers in the substrate 110—which define sense anddrive electrodes of the touch sensor—can include thinner layers of theconductive material.

4.3 Inductor Control Circuit and Coil Drivers

The substrate 110 also includes an inductor control circuit—such aspatterned across the first (i.e., bottom) conductive layer—and extendingto each inductor 120. For example, the substrate 110 can includemultiple (e.g., six) inductor 120 rows, wherein each inductor 120 rowincludes multiple inductors 120. For each inductor 120 row, the inductorcontrol circuit includes a row trace connecting first pins of eachinductor 120 in this row in parallel. The inductor control circuit canalso include a set of column traces, each connecting second pins ofmultiple inductors 120—spanning multiple inductor 120 rows—in parallel.In particular, a column trace can connect the second pins of a group ofinductors 120 in parallel, wherein this group of inductors 120 includesno more than one inductor 120 from each inductor 120 row.

Furthermore, the row and column traces can terminate at a set of coildriver 171 pads, such as on the first conductive layer of the substrate110 opposite the force-sensitive layer 160. A set of coil drivers 171can be installed on these coil driver 171 pads, and each coil driver 171can be configured to selectively energize one inductor 120 in the groupof inductors 120 connected thereto by the inductor control circuit.

In one implementation, the inductor control circuit includes multiplerow and column traces, wherein each pair of row and column tracesconnects first and second pins, respectively, of up to a limitedquantity (e.g., four) inductors 120 to one coil driver 171. In thisimplementation, one coil driver 171 can be connected to this limitedquantity of inductors 120 located at key locations 132 characterized bylow probability of concurrent selection by a user. For example, an“alphanumerical group” of inductors 120—connected to one coil driver 171via the inductor control circuit—can include one inductor 120 pairedwith a numerical key, two inductors 120 paired with alphabetical keys,and one inductor 120 paired with a “function” (e.g., “F1,” . . . ,“F12”) key. The keyboard system 100 can thus include multiple (e.g.,thirteen) similar alphanumerical inductor 120 groups, each connected toone coil driver 171. In this example, a first “keyboard modifier group”of inductors 120—connected to another coil driver 171 via the inductorcontrol circuit—can include two inductors 120 paired with two “SHIFT”keys, one inductor 120 paired with a “CAPS LOCK” key, and one inductor120 paired with an “escape” key. A second “keyboard modifier group” ofinductors 120—connected to yet another coil driver 171 via the inductorcontrol circuit—can include two inductors 120 paired with two “COMMAND”keys and two inductors 120 paired with two punctuation keys. A third“keyboard modifier group” of inductors 120—connected to another coildriver 171 via the inductor control circuit—can include two inductors120 paired with two “OPTION” keys, one inductor 120 paired with a“POWER” key, and one inductor 120 paired with a punctuation key. Afourth “keyboard modifier group” of inductors 120—connected to yetanother coil driver 171 via the inductor control circuit—can include oneinductor 120 paired with a “CONTROL” key, one inductor 120 paired with a“LINE RETURN” key, and one inductor 120 paired with a punctuation key. Afifth “keyboard modifier group” of inductors 120—connected to anothercoil driver 171 via the inductor control circuit—can include oneinductor 120 paired with a “DELETE” key, one inductor 120 paired with a“SPACEBAR” key, and two inductors 120 paired with two remainingpunctuation keys. A sixth “navigation group” of inductors 120—connectedto another coil driver 171 via the inductor control circuit—can includefour inductors 120 paired with each of four left, right, up, and downnavigation keys.

The controller 170 can therefore initiate a haptic feedback cycle at aparticular inductor 120 in the security technology—in response todepression of a corresponding key—by: selecting a particular coil driver171 connected to a group of inductors 120 containing the particularinductor 120; sending a particular address of the particular inductor120 in this group to the particular coil driver 171; and triggering theparticular coil driver 171 to output an alternating signal to thisparticular address. Accordingly, the particular coil driver 171 can:connect a row trace coupled to the first pin of the particular inductor120 to an alternating power source; connect a column trace coupled tothe second pin of the particular inductor 120 to the alternating powersource; and disconnect (or “float”) all other row and column traces inthe group in order to solely energize the particular inductor 120, whichthus magnetically couples to and oscillates the magnetic element 150 inthe adjacent key.

However, inductors 120 in the set can be grouped according to any otherschema, can be connected to one or more coil drivers 171 in any otherformat, and can be selectively polarized by the coil driver 171(s) inany other way during a haptic feedback cycle.

5. Force-Sensitive Layer

As described above, the force-sensitive layer 160: is arranged acrossthe array of drive electrode and sense electrode pairs 112 on the toplayer 115 of the substrate 110; and defines a force-sensitive materialexhibiting variations in local bulk resistance and/or local contactresistance as a function of compression between a key and the substrate110—and therefore as a function of force applied to a key arranged overthe force-sensitive layer 160. The force-sensitive layer 160 and thedrive electrode and sense electrode pairs 112 on the top layer 115 ofthe substrate 110 can thus cooperate to form a touch sensor.

In one implementation, the perimeter of the force-sensitive layer 160 isretained against the substrate 110 via a frame and/or an adhesive.Additionally or alternatively, the force-sensitive layer 160 can bebonded to the substrate 110, such as selectively at interstitial areason the top surface of the substrate 110 between drive electrode andsense electrode pairs 112. In another implementation, theforce-sensitive layer 160 is mechanically retained against the substrate110 near each key location 132 by retention posts 142 (or “shoulderpins”) extending from each key through corresponding perforations in theforce-sensitive layer 160 and the substrate 110, as described below.

However, the force-sensitive layer 160 can be arranged over and coupledto the substrate 110 in any other way.

6. Keys

The keyboard system 100 can further include a set of discrete keyelements 140 (or “keys”), each: arranged over the force-sensitive layer160; centered over an inductor 120 at a key location 132; and includinga magnetic element 150 configured to magnetically couple to the adjacentinductor 120. Generally, the set of keys cooperate to from a tactilelayer 130 that, when depressed by a user, returns local, key-specifichaptic (e.g., vibratory) feedback to confirm keystrokes entered atindividual keys.

6.1 Pinned Key Connection

In one implementation shown in FIGS. 1-3 , each key defines a discretestructure, including a rigid polymer (e.g., polycarbonate, nylon)overmolded around a magnetic element 150. In this implementation, eachdiscrete key can include: a top (i.e., outer) tactile surface; and a setof retention posts 142 (e.g., four shoulder pins including a narrow necksection and a widened head section) extending downward from the cornersof the key opposite the tactile surface. In this implementation, theforce-sensitive layer 160 defines a continuous layer extending acrossthe top of the substrate 110, and the substrate 110 and theforce-sensitive layer 160 each include a set of (e.g., four)through-bores around the inductor 120 at each key location 132. Duringassembly, the force-sensitive layer 160 is arranged over the substrate110 with its through-bores aligned with corresponding through-bores inthe substrate 110 at each key location 132. The retention posts 142 of akey are then inserted through the through-bores in the force-sensitivelayer 160 such that the heads of these shoulder pins engage the bottomsurface of the substrate 110, thereby retaining the key and the adjacentregion of the force-sensitive layer 160 against the substrate 110. Otherkeys in the set are similarly assembled onto the substrate 110 at eachother key location 132 to form a complete keyboard.

6.1.1 Horizontal Magnetic Element Configuration

In the foregoing implementation, the magnetic element 150 in a key canbe arranged in a horizontal orientation with N-S ends of the magneticelement 150 located proximal two opposing sides of the key, as shown inFIG. 3 . In this implementation, because a magnetic field generated byan inductor 120 passes through the center of the inductor 120 and thusnormal to the top of the substrate 110, this horizontal orientation ofthe magnetic element 150 in the key may cause the key to oscillate(predominantly) in a direction parallel to the top surface of thesubstrate 110. Thus, in this implementation, the through-bores in thesubstrate 110 and force-sensitive layer 160 can be oversized for theneck sections of the retention posts 142 by a radial lengthapproximating an oscillation amplitude of the key (e.g., 100 microns)such that pins can shift laterally within their bores with minimalobstruction as the key oscillates over the force-sensitive layer 160when the corresponding inductor 120 is polarized during a hapticfeedback cycle. Similarly, the perimeter of the key can be offset fromthe perimeters of adjacent keys by this oscillation amplitude, therebyenabling the key to oscillate without obstruction by these adjacent keyswhen the corresponding inductor 120 is polarized during a hapticfeedback cycle.

Additionally or alternatively, in the foregoing implementation, elasticbumpers (e.g., low-durometer sleeves or grommets): can be installed inthe through-bores in the substrate 110; can deform to accommodatemovement of the retention post 142 within these through-bores as the keyoscillates during a haptic feedback cycle; and can re-center the keyover its key location 132 following conclusion of the haptic feedbackcycle. Alternatively, the through-bores in the substrate 110 can beoversized for the neck sections of the retention posts 142 as describedabove; and the force-sensitive layer 160 can include an elasticsubstrate 110 material, can include through-bores sized for a close(e.g., running) fit around the necks of the retention posts 142 of thekey, and deform around these retention posts 142 when the key isoscillation during a haptic feedback cycle, and can re-center the keyover the key location 132 following conclusion of the haptic feedbackcycle.

Yet alternatively, in this implementation, a key can include a set ofelastic retention posts 142. For example, the body and retention posts142 can be formed in an elastic material (e.g., silicone rubber)overmolded around the magnetic element 150. In this implementation: thethrough-bores in the substrate 110 can be sized for a close (e.g.,running) fit around the necks of the retention posts 142 of the key; thethrough-bores in the force-sensitive layer 160 can be sized for a loosefit around the necks of the retention posts 142 of the key; and theelastic retention posts 142 can elastically deform to accommodateoscillation of the key during a haptic feedback cycle.

6.1.2 Vertical Magnetic Element Configuration

Alternatively, the magnetic element 150 in a key can be arranged in avertical orientation with N-S axis of the magnetic element 150 extendingnormal to the top surface of the substrate 110 and approximatelycentered over the corresponding inductor 120 at a key location 132, asshown in FIG. 1 . In this implementation, because the magnetic fieldgenerated by the inductor 120 passes through the center of the inductor120 and thus normal to the top of the substrate 110, this verticalorientation of the magnetic element 150 in the key may cause the key tooscillate (predominantly) in a direction normal to the top surface ofthe substrate 110.

Thus, in this implementation, a key can include a set of elasticretention posts 142, such as described above, configured to elasticallyelongate in order to accommodate oscillation of the key during a hapticfeedback cycle. Additionally or alternatively, these pins can extendrearward from the corners of the key, and the body of the key can bethin, elastic, and/or include a flexure that enables a center of the keycontaining the magnetic element 150 to oscillate vertically while thecorners of the key are retained by the retention posts 142 and thusremain approximately static (e.g., exhibit less oscillation) during ahaptic feedback cycle.

Alternatively, in this implementation: a key can include a pin with ahead that extends below the bottom of the substrate 110 when installedthrough bores in the force-sensitive layer 160 and substrate 110 at akey location 132; and a spring (e.g., a coil spring, an elastic grommet)can be installed between the head of the pin and the bottom surface ofthe substrate 110. The spring can thus accommodate vertical oscillationof the key during a haptic feedback cycle; and draw the key downwardtoward the substrate 110 and retain the force-sensitive layer 160against the substrate 110 following conclusion of a haptic feedbackcycle.

6.2 Adhesive Key Integration

In another implementation, a discrete key can be bonded to theforce-sensitive layer 160, such as with a flexible adhesive that yieldsin shear to accommodate oscillation of the key relative to theforce-sensitive layer 160 during a haptic feedback cycle.

In a similar implementation, the set of keys are molded into a singlekey assembly that includes flexures (or bellow or other structuresconfigured to accommodate relative motion) between adjacent keys. Inthis implementation, regions of the key assembly between these keys canbe bonded to the force-sensitive layer 160 or mechanically connected tothe force-sensitive layer 160 and substrate 110, such as via pinnedconnections as described above. Thus, in this implementation, theseregions of the key assembly between keys can form a flexible “frame”around these keys, and the keys can oscillate individually within theframe during haptic feedback cycles.

6.3 Frame Integration

Alternatively, the keyboard system 100 can include a rigid frame (e.g.,an aluminum frame): defining an aperture at each key location 132;configured to install over the force-sensitive layer 160; and configuredto locate and retain each key over its key location 132, as shown inFIG. 4 . In this implementation, a key can include a shoulder extendingoutwardly about the perimeter of its base, and the frame can retain thisshoulder about the perimeter of the aperture housing the key.

In this implementation, for the key that includes a magnetic element 150in the horizontal magnetic element 150 configuration, an aperture canalso be oversized laterally for the body of the key above theshoulder—such as by the oscillation amplitude of the key—in order toenable the key to oscillate laterally during a haptic feedback cycle.

Conversely, for the key that includes a magnetic element 150 in thevertical magnetic element 150 configuration, the interior face of theframe around an aperture can be offset above the force-sensitive layer160 by the sum of the thickness of the key shoulder and oscillationamplitude of the key in order to enable the key to oscillate verticallyduring a haptic feedback cycle. (In this implementation, the keyboardsystem 100 can also include a spring between the key and the frame inorder to bias the key against the force-sensitive layer 160 or betweenthe key and the force-sensitive layer 160 in order to bias the keyagainst the frame while also enabling the key to oscillation verticallyduring a haptic feedback cycle.)

However, a key can be coupled to and retained over the force-sensitivelayer 160 and substrate 110 in any other way.

7. Illumination

In one variation shown in FIGS. 1-4 , the substrate 110 further includesan array of light elements 180 (e.g., LEDs), including one light element180 at each key location 132, configured to illuminate the set of keys.

In one implementation, the top of the substrate 110 is relieved proximalthe center of the inductor 120 at each key location 132 to form a recessand expose the second conductive layer (over the first structural layerof the substrate 110) in the recess. In particular, each recess can besized for a surface-mount LED, and the second conductive layer of thesubstrate 110 can include pads configured to mount the surface-mountLED. During assembly, surface-mount LEDs can be installed in each recessand soldered to the pads within these recesses such that the top of thelight element 180 is flush with or falls below the top surface of thesubstrate 110. Furthermore, in this implementation, the force-sensitivelayer 160 can form a translucent structure (e.g., translucent siliconerubber supporting a matrix of conductive particulate). Similarly, eachkey can be formed in a translucent material or include a light pipe 182aligned with the light element 180 such that light passing through theforce-sensitive layer 160 illuminates the key (similar to as shown inFIG. 9 ).

In another implementation shown in FIGS. 3 and 4 , a surface mount LEDis installed on the top conductive layer of the substrate 110 at eachkey location 132, such as approximately centered over a correspondinginductor 120. In this implementation, the force-sensitive layer 160 isperforated at each LED location, and each key is formed in a translucentmaterial or includes a light pipe 182 aligned with the light element 180(e.g., through a center of the magnetic element 150 defining an annularmagnet) such that light emitted by the light element 180 illuminates thetop of the key.

In yet another implementation, the substrate 110 and force-sensitivelayer 160 are perforated at each key location 132, such as with one or aset of perforations located inside of the spiral traces formed by theinductor 120 at each key location 132. In this implementation, a lightsource is arranged across or near the bottom face of the substrate 110,such as including one light element 180 per key location 132 or clusterof key locations 132. In this implementation, each key can be formed ina translucent material or include a light pipe 182 aligned with anadjacent perforation in the force-sensitive layer 160 and substrate 110such that light output below the substrate 110 passed through thesubstrate 110 and force-sensitive layer 160 to illuminate the key.

In a similar implementation shown in FIGS. 1 and 2 , in the variationdescribed above in which a key includes a set of pins that pass throughthe substrate 110 and the force-sensitive layer 160, the pins can beformed in a translucent material to form light pipes 182, and a lightsource can be arranged across the bottom face of the substrate 110.Thus, the pins of this key can transmit light—emitted by this lightsource—through the substrate 110 and force-sensitive layer 160 toilluminate the key.

However, the keyboard system 100 can include any other key and lightsource configuration to illuminate these keys.

8. Chassis Installation

The substrate 110—overlayed with the force-sensitive layer 160 andkeys—can be installed in a keyboard receptacle of a computing device,such as by rigidly fastening or bonding the perimeter of the substrate110 to a perimeter of the receptacle.

However, the substrate 110 can be installed or mounted to a chassis inany other way.

9. Controller

The controller 170 is configured to: scan electrical values (e.g.,resistances) between drive electrode and sense electrode pairs 112 inthe substrate 110; interpret a force magnitude and a location of aninput across the set of keys based on changes in electrical valuesbetween a subset of these drive electrode and sense electrode pairs 112;interpret a keystroke value corresponding to a particular key proximalthe location of this input and output this keystroke value (e.g., to aconnected computer) if the force magnitude of the input exceeds athreshold force magnitude; and trigger a coil driver 171 to output analternating current to a particular inductor 120 adjacent the particularkey in order to vibrate the particular key—such as for a period of 100milliseconds beginning within 10 milliseconds of detecting the input atthe particular key—during a haptic feedback cycle. A user depressing theparticular key with a finger may thus tactilely perceive resultingoscillation of the particular key as depression of the particularkey—similar to a mechanical “snap” button—below her finger.

More specifically and as described above, the substrate 110 can includea drive electrode and sense electrode pair 112 below each key of thekeyboard; and the force-sensitive layer 160 can be arranged between thesubstrate 110 and the set of keys, can bridge gaps between these driveelectrode and sense electrode pairs 112, and can exhibit variableresistance between each drive electrode and sense electrode pair 112 asa function of downward force applied to the corresponding key. Forexample, depression of a particular key can compress a particular regionof the force-sensitive layer 160 under the key against the particulardrive electrode and sense electrode pair 112 located under this key,thereby reducing the resistance between the particular drive electrodeand sense electrode pair 112—bridged by this region of theforce-sensitive layer 160—and increasing the voltage at the senseelectrode when the drive electrode is driven to a reference or nominalvoltage.

Thus, during a scan cycle, the controller 170 can read electrical valuesfrom the array of electrodes by: driving these drive electrodes with areference voltage; and reading sense voltages from these senseelectrodes. The controller 170 can then register a keystroke on a firstkey during this scan cycle in response to a first sense voltage—readfrom a first sense electrode—differing from a stored baseline voltagefor the first sense electrode, such as by more than a first thresholdvoltage that corresponds to a minimum keystroke force assigned to thefirst key (e.g., 165 grams). Accordingly, the controller 170 can executea first haptic feedback cycle at the first key by driving a firstinductor 120—located under the first key—with an oscillating voltage,thereby: causing the first inductor 120 to generate an oscillatingmagnetic field, which interacts with and oscillates a first magneticelement 150 in the first key independently of all other keys within thekeyboard; and haptically indicates to a user that the controller 170registered a keystroke at the first key.

Then, during a later (e.g., a next) scan cycle), the controller 170 can:drive the drive electrodes at each key location 132 with a referencevoltage; read a second set of sense voltages (i.e., “electrical values”)from these sense electrodes; and register release of the first keystrokefrom the first key in response to a second sense voltage—read from thefirst sense electrode during the second scan cycle—differing from thestored baseline voltage for the first sense electrode by less than asecond threshold voltage, such as less than the first threshold voltage.Accordingly, the controller 170 can execute a second haptic feedbackcycle at the first key by driving the first inductor 120—located underthe first key—with an oscillating voltage, thereby: again causing thefirst inductor 120 to generate an oscillating magnetic field, whichinteracts with and oscillates the first magnetic element 150 in thefirst key independently of all other keys within the keyboard; andhaptically indicates to the user that the controller 170 registered arelease of the first key.

In particular, the controller 170 can implement different thresholdelectrical value changes to detect selection and release of these keysin order to avoid repetitive haptic feedback cycles (or “bounce,”“jitter”) at keys when a user depresses these keys with consistentforces around the minimum keystroke forces assigned to these keys. Forexample, the controller 170 can: implement a first threshold electricalvalue change—corresponding to a minimum keystroke force of 165 grams—todetect selection of keys in the keyboard; and then drive inductors 120corresponding to these keys with oscillating signals of a firstamplitude and a second frequency that generates key vibration physicallyor tactilely analogous to collapse of a mechanical dome switch ormechanical key. In this example, the controller 170 can also: implementa second threshold electrical value change—less than the first thresholdelectrical value change and corresponding to a maximum key release forceof 100 grams—to detect release of keys in the keyboard; and then driveinductors 120 corresponding to these keys with oscillating signals of asecond amplitude and frequency (e.g., less than the first amplitude andgreater than the first frequency) and that generates key vibrationphysically or tactilely analogous to rise of a mechanical dome switch ormechanical key.

9.1 Selective Keystroke Sensing

Furthermore, because polarization of an inductor 120 may induceelectrical noise in an adjacent drive electrode and sense electrode pair112, the controller 170 can also selectively skip or disable sampling ofa particular drive electrode and sense electrode pair 112 arranged overthe inductor 120 (and/or particular row and column traces coupled to theparticular drive electrode and sense electrode pair 112) during andimmediately after the haptic feedback cycle (e.g., as the particularinductor 120 depth sensor-energizes). Additionally or alternatively, thecontroller 170 can continue to sample all drive electrode and senseelectrode pairs 112 in the touch sensor during the haptic feedback cyclebut discard all additional inputs interpreted at the particular driveelectrode and sense electrode pair 112 during and immediately after thehaptic feedback cycle. Yet alternatively, the controller 170 cancontinue to sample all drive electrode and sense electrode pairs 112 inthe touch sensor during the haptic feedback cycle but increase athreshold force for interpreting an input at the particular driveelectrode and sense electrode pair 112 in order to reduce sensitivity tonoise at the particular drive electrode and sense electrode pair 112during and immediately after the haptic feedback cycle.

10. Multi-Layer Inductor

As described above and shown in FIGS. 2 and 8 , the keyboard systemincludes a multi-layer inductor 120—formed by a set of interconnectedspiral traces fabricated directly within conductive layers within thesubstrate 110—under each key location 132.

Generally, the total inductance of a single spiral trace may be limitedby the thickness of the conductive layer. Therefore, the keyboard systemcan include a stack of overlapping, interconnected spiral tracesfabricated on a set of adjacent layers of the substrate 110 to form amulti-layer, multi-turn, and/or multi-core inductor 120 that exhibitsgreater inductance—and therefore greater magnetic coupling to the set ofmagnetic elements 150—than a single spiral trace on a single conductivelayer of the substrate 110. These spiral traces can be coaxially alignedabout a common vertical axis (e.g., centered over the set of magneticelements 150) and electrically interconnected by a set of vias throughthe intervening layers of the substrate 110.

Furthermore, the substrate 110 can include conductive layers ofdifferent thicknesses. Accordingly, spiral traces within thickerconductive layers of the substrate 110 can be fabricated with narrowertrace widths and more turns, and spiral traces within thinner conductivelayers of the substrate 110 can be fabricated with wider trace widthsand fewer turns in order to achieve similar electrical resistanceswithin each spiral trace over the same coil footprint. For example,lower conductive layers within the substrate 110 can include heavierlayers of conductive material (e.g., one-ounce copper approximately 35microns in thickness) in order to accommodate narrower trace widths andmore turns within the coil footprint in these conductive layers, therebyincreasing inductance of each spiral trace and yielding greater magneticcoupling between the multi-layer inductor 120 and the set of magneticelements 150 during a haptic feedback cycle. Conversely, in thisexample, the upper layers of the substrate 110—which include driveelectrode and sense electrode pairs 112 of the touch sensor—can includethinner layers of conductive material.

10.1 Single Core+Even Quantity of Coil Layers

In one implementation, the substrate 110 includes an even quantity ofspiral traces fabricated within an even quantity of layers within thesubstrate 110 to form a single-coil inductor 120 under a key of thekeyboard.

In one example, the substrate 110 includes: a top layer 115 and anintermediate layer containing the array of drive electrode and senseelectrode pairs 112; a first layer 116; a second layer 117; a thirdlayer 118; and a fourth (e.g., a bottom) layer. In this example, thefirst layer 116 includes a first spiral trace 121 coiled in a firstdirection and defining a first end and a second end. In particular, thefirst spiral trace 121 can define a first planar coil spiraling inwardlyin a clockwise direction from the first end at the periphery of thefirst planar coil to the second end proximal a center of the firstplanar coil. The second layer 117 includes a second spiral trace 122coiled in a second direction opposite the first direction and defining athird end—electrically coupled to the second end of the first spiraltrace 121—and a fourth end. In particular, the second spiral trace 122can define a second planar coil spiraling outwardly in the clockwisedirection from the third end proximal the center of the second planarcoil to the fourth end at a periphery of the second planar coil.

Similarly, the third layer 118 includes a third spiral trace 123 coiledin the first direction and defining a fifth end—electrically coupled tothe fourth end of the second spiral trace 122—and a sixth end. Inparticular, the third spiral trace 123 can define a third planar coilspiraling inwardly in the clockwise direction from the fifth end at theperiphery of the third planar coil to the sixth end proximal a center ofthe third planar coil. Furthermore, the fourth layer includes a fourthspiral trace 124 coiled in the second direction and defining a seventhend—electrically coupled to the sixth end of the first spiral trace121—and an eighth end. In particular, the fourth spiral trace 124 candefine a fourth planar coil spiraling outwardly in the clockwisedirection from the seventh end proximal the center of the fourth planarcoil to the eighth end at a periphery of the fourth planar coil.

Accordingly: the second end of the first spiral trace 121 can be coupledto the third end of the second spiral trace 122 by a first via; thefourth end of the second spiral trace 122 can be coupled to the fifthend of the third spiral trace 123 by a second via; the sixth end of thethird spiral trace 123 can be coupled to the seventh end of the fourthspiral trace 124 by a third via; and the first, second, third, andfourth spiral traces 121, 122, 123, 124 can cooperate to form asingle-core, four-layer inductor 120. The controller 170 (or a driver):can be electrically connected to the first end of the first spiral trace121 and the eighth end of the fourth spiral trace 124 (or “terminals” ofthe multi-layer inductor 120); and can drive these terminals of themulti-layer inductor 120 with an oscillating voltage during a hapticfeedback cycle in order to induce an alternating magnetic field throughthe multi-layer inductor 120, which couples to the magnetic element 150in the key (or tactile layer 130) above and oscillates the key (or alocal region of the tactile layer 130) over the substrate 110. Inparticular, when the controller 170 drives the multi-layer inductor 120at a first polarity, current can flow in a continuous, clockwisedirection through the first, second, third, and fourth spiral traces121, 122, 123, 124 to induce a magnetic field in a first directionaround the multi-layer inductor 120. When the controller 170 reversesthe polarity across terminals of the multi-layer inductor 120, currentcan reverse directions and flow in a continuous, counter-clockwisedirection through the first, second, third, and fourth spiral traces121, 122, 123, 124 to induce a magnetic field in a second, oppositedirection at the multi-layer inductor 120.

Furthermore, in this implementation, because the multi-layer inductor120 spans an even quantity of conductive layers within the substrate110, the terminals of the multi-layer inductor 120 can be located on theperipheries of the first and last layers of the substrate 110 and thusenable direct connection to the controller 170 (or other driver).

10.2 Single Core+Odd Quantity of Coil Layers

In another implementation shown in FIG. 2 , the multi-layer inductor 120spans an odd number of (e.g., 3, 5) conductive layers of the substrate110. In this implementation, a conductive layer of the substrate 110 caninclude two parallel and offset spiral traces that cooperate with otherspiral traces in the multi-layer inductor 120 to locate the terminals ofthe multi-layer inductor 120 at the periphery of the multi-layerinductor 120 for direct connection to the controller 170 or driver.

In one example, the substrate 110 includes: a top layer 115 and anintermediate layer containing the array of drive electrode and senseelectrode pairs 112; a first layer 116; a second layer 117; a thirdlayer 118; and a fourth (e.g., a bottom) layer. In this example, thefirst layer 116 includes a ground electrode 119 (e.g., a continuoustrace): spanning the footprint of the array of drive electrode and senseelectrode pairs 112 in the top and intermediate layers; driven to areference potential by the controller 170; and configured to shield thedrive electrode and sense electrode pair 112 at each key location 132from electrical noise generated by the adjacent multi-layer inductors120.

In this example, the third layer 118 includes a first spiral trace 121coiled in a first direction and defining a first end and a second end.In particular, the first spiral trace 121 can define a first planar coilspiraling inwardly in a clockwise direction from the first end at theperiphery of the first planar coil to the second end proximal a centerof the first planar coil. The second layer 117 includes a second spiraltrace 122 coiled in a second direction opposite the first direction anddefining a third end—electrically coupled to the second end of the firstspiral trace 121 in the third layer 118—and a fourth end. In particular,the second spiral trace 122 can define a second planar coil spiralingoutwardly in the clockwise direction from the third end proximal thecenter of the second planar coil to the fourth end at a periphery of thesecond planar coil.

The third layer 118 further includes a third spiral trace 123 coiled inthe first direction and defining a fifth end—electrically coupled to thefourth end of the second spiral trace 122 in the second layer 117—and asixth end. In particular, the third spiral trace 123 can define a thirdplanar coil: spiraling inwardly in the clockwise direction from thefifth end at the periphery of the third planar coil to the sixth endproximal a center of the third planar coil; and nested within the firstplanar coil that also spirals inwardly in the clockwise direction withinthe third layer 118.

Furthermore, the fourth layer includes a fourth spiral trace 124 coiledin the second direction and defining a seventh end—electrically coupledto the sixth end of the first spiral trace 121—and an eighth end. Inparticular, the fourth spiral trace 124 can define a fourth planar coilspiraling outwardly in the clockwise direction from the seventh endproximal the center of the fourth planar coil to the eighth end at aperiphery of the fourth planar coil.

Accordingly: the second end of the first spiral trace 121 within thethird layer 118 can be coupled to the third end of the second spiraltrace 122 within the second layer 117 by a first via; the fourth end ofthe second spiral trace 122 within the second layer 117 can be coupledto the fifth end of the third spiral trace 123 within the third layer118 by a second via; the sixth end of the third spiral trace 123 withinthe third layer 118 can be coupled to the seventh end of the fourthspiral trace 124 within the fourth layer by a third via; and the first,second, third, and fourth spiral traces 121, 122, 123, 124 can cooperateto form a single-core, three-layer inductor 120. The controller 170: canbe electrically connected to the first end of the first spiral trace 121within the third layer 118 and the eight end of the fourth spiral trace124 within the fourth layer (or “terminals” of the multi-layer inductor120); and can drive these terminals of the multi-layer inductor 120 withan oscillating voltage during a haptic feedback cycle in order to inducean alternating magnetic field through the multi-layer inductor 120,which couples to the magnetic element 150 in the key (or tactile layer130) above and oscillates the key (or a local region of the tactilelayer 130) over the substrate 110. In particular, when the controller170 drives the multi-layer inductor 120 at a first polarity, current canflow in a continuous, clockwise direction through the first, second,third, and fourth spiral traces 121, 122, 123, 124 within the second,third, and fourth layers of the substrate 110 to induce a magnetic fieldin a first direction around the multi-layer inductor 120. When thecontroller 170 reverses the polarity across terminals of the multi-layerinductor 120, current can reverse directions and flow in a continuous,counter-clockwise direction through the first, second, third, and fourthspiral traces 121, 122, 123, 124 to induce a magnetic field in a second,opposite direction at the multi-layer inductor 120.

Therefore, in this implementation, the substrate 110 can include an evennumber of single-coil layers and an odd number of two-coil layersselectively connected to form a multi-layer inductor 120 that includestwo terminals located on the periphery of the multi-layer inductor 120at each key location 132.

10.3 Double Core+Even Quantity of Coil Layers

In another implementation shown in FIG. 8 , the substrate 110 includesan even quantity of spiral traces fabricated within an even quantity oflayers within the substrate 110 to form a dual-core inductor 120 (thatis, two separate single-core inductors 120 connected in series).

In one example, the substrate 110 includes: a top layer 115 and anintermediate layer containing the array of drive electrode and senseelectrode pairs 112; a first layer 116; a second layer 117; a thirdlayer 118; and a fourth (e.g., a bottom) layer.

In this example, the first layer 116 includes a first spiral trace 121coiled in a first direction and defining a first end and a second end.In particular, the first spiral trace 121 can define a first planar coilspiraling inwardly in a clockwise direction from the first end at theperiphery of the first planar coil to the second end proximal a centerof the first planar coil. The second layer 117 includes a second spiraltrace 122 coiled in a second direction opposite the first direction anddefining a third end—electrically coupled to the second end of the firstspiral trace 121—and a fourth end. In particular, the second spiraltrace 122 can define a second planar coil spiraling outwardly in theclockwise direction from the third end proximal the center of the secondplanar coil to the fourth end at a periphery of the second planar coil.The third layer 118 includes a third spiral trace 123 coiled in thefirst direction and defining a fifth end—electrically coupled to thefourth end of the second spiral trace 122—and a sixth end. Inparticular, the third spiral trace 123 can define a third planar coilspiraling inwardly in the clockwise direction from the fifth end at theperiphery of the third planar coil to the sixth end proximal a center ofthe third planar coil. Furthermore, the fourth layer includes a fourthspiral trace 124 coiled in the second direction and defining a seventhend—electrically coupled to the sixth end of the first spiral trace121—and an eighth end. In particular, the fourth spiral trace 124 candefine a fourth planar coil spiraling outwardly in the clockwisedirection from the seventh end proximal the center of the fourth planarcoil to the eighth end at a periphery of the fourth planar coil.

Accordingly: the second end of the first spiral trace 121 can be coupledto the third end of the second spiral trace 122 by a first via; thefourth end of the second spiral trace 122 can be coupled to the fifthend of the third spiral trace 123 by a second via; the sixth end of thethird spiral trace 123 can be coupled to the seventh end of the fourthspiral trace 124 by a third via; and the first, second, third, andfourth spiral traces 121, 122, 123, 124 can cooperate to form a firstsingle-core, four-layer inductor 120.

Furthermore, in this example, the first layer 116 includes a fifthspiral trace adjacent the first spiral trace 121, coiled in the seconddirection, and defining a ninth end—coupled to the first end of thefirst planar coil—and a tenth end. In particular, the fifth spiral tracecan define a fifth planar coil spiraling inwardly in a clockwisedirection from the ninth end at the periphery of the fifth planar coilto the tenth end proximal a center of the fifth planar coil. The secondlayer 117 includes a sixth spiral trace adjacent the second spiral trace122, coiled in the first direction, and defining an eleventhend—electrically coupled to the tenth end of the fifth spiral trace—anda twelfth end. In particular, the sixth spiral trace can define a sixthplanar coil spiraling outwardly in the clockwise direction from theeleventh end proximal the center of the sixth planar coil to the twelfthend at a periphery of the sixth planar coil. The third layer 118includes a seventh spiral trace adjacent the third spiral trace 123,coiled in the second direction, and defining a thirteenthend—electrically coupled to the twelfth end of the sixth spiraltrace—and a fourteenth end. In particular, the seventh spiral trace candefine a seventh planar coil spiraling inwardly in the clockwisedirection from the thirteenth end at the periphery of the seventh planarcoil to the fourteenth end proximal a center of the seventh planar coil.Furthermore, the fourth layer includes an eighth spiral trace adjacentthe fourth spiral trace 124, coiled in the first direction, and defininga fifteenth end—electrically coupled to the fourteenth end of theseventh spiral trace—and a sixteenth end. In particular, the eighthspiral trace can define an eighth planar coil spiraling outwardly in theclockwise direction from the fifteenth end proximal the center of theeighth planar coil to the sixteenth end at a periphery of the eighthplanar coil.

Accordingly: the tenth end of the fifth spiral trace can be coupled tothe eleventh end of the sixth spiral trace by a fourth via; the twelfthend of the sixth spiral trace can be coupled to the thirteenth end ofthe seventh spiral trace by a fifth via; the fourteenth end of theseventh spiral trace can be coupled to the fifteenth end of the eighthspiral trace by a sixth via; and the fifth, sixth, seventh, and eighthspiral traces can cooperate to form a second single-core, four-layerinductor 120.

Furthermore, the first end of the first spiral trace 121 can be coupledto (e.g., form a continuous trace with) the ninth end of the fifthspiral trace within the first conductive layer. The first and secondsingle-core, four-layer inductors 120 can therefore be fabricated inseries to form a four-layer, dual-core inductor 120 with the eighth andsixteenth ends of the fourth and eighth spiral traces, respectively,forming the terminals of the four-layer, dual-core inductor 120.Therefore, when these first and second multi-layer inductors 120 aredriven to a first polarity, current can flow in a continuous circulardirection through both the first multi-layer inductor 120 such that thefirst and second multi-layer inductors 120 produce magnetic fields inthe same phase and in the same direction.

The controller 170 (or a driver): can be electrically connected to theseterminals and can drive these terminals with an oscillating voltageduring a haptic feedback cycle in order to induce: a first alternatingmagnetic field through the first single-core, four-layer inductor 120(formed by the first, second, third, and fourth spiral traces 121, 122,123, 124); and a second alternating magnetic field—in phase with thefirst alternating magnetic field—through the second single-core,four-layer inductor 120 (formed by the fifth, sixth, seventh, and eighthspiral traces). In particular, when the controller 170 drives thefour-layer, dual-core inductor 120 at a first polarity, current canflow: in a continuous, clockwise direction through the first, second,third, and fourth spiral traces 121, 122, 123, 124 to induce a magneticfield in a first direction around the first single-core, four-layerinductor 120; and in a continuous, clockwise direction through thefifth, sixth, seventh, and eighth spiral traces to induce a magneticfield in the first direction around the second single-core, four-layerinductor 120. When the controller 170 reverses the polarity acrossterminals of the dual-core, four-layer inductor 120, current can reversedirections to: flow in a continuous, counter-clockwise direction throughthe first, second, third, and fourth spiral traces 121, 122, 123, 124 toinduce a magnetic field in a second, opposite direction around the firstsingle-core, four-layer inductor 120; and in a continuous,counter-clockwise direction through the fifth, sixth, seventh, andeighth spiral traces to induce a magnetic field in the second directionaround the second single-core, four-layer inductor 120.

10.4 Double Core+Odd Quantity of Coil Layers

In a similar implementation, the substrate 110 includes an odd quantityof spiral traces fabricated within an odd quantity of layers within thesubstrate 110 to form a dual-core inductor 120.

For example, in this implementation, the dual-core inductor 120 caninclude two single-coil, three-layer inductors 120 connected in series.In this example, each single-coil, three-layer inductor 120 includes: aneven number of single-coil layers; and an odd number of two-coil layersselectively connected to form a single-coil, three-layer inductor 120that includes two terminals located on the periphery of the single-coil,three-layer inductor 120, as described above.

10.5 Horizontal Oscillation: Single-Core Multi-Layer Inductor

Generally, the keyboard system includes a set of magnetic elements 150,each: arranged within an individual key (or within a key location 132 ofthe tactile layer 130); and configured to magnetically couple to thecorresponding multi-layer inductor 120 in the substrate 110 below duringa haptic feedback cycle, thereby oscillating the individual key (or thekey location 132 of the tactile layer 130) during a haptic feedbackcycle.

In one implementation, each magnetic element 150 is arranged in a singlekey (or key location 132 in the tactile layer 130) relative to itscorresponding multi-layer inductor 120 such that this multi-layerinductor 120 induces an oscillating force on the magnetic element 150parallel to the substrate 110, thereby horizontally vibrating thecorresponding individual key (or the individual key location 132 of thetactile layer 130) during a haptic feedback cycle, as shown in FIG. 9 .

In this implementation, a key (or individual key location 132 within thetactile layer 130) can include a first magnet 151: embedded orovermolded within the key (or key location 132); defining a firstmagnetic polarity facing the corresponding multi-layer inductor 120below; and extending along a first side of the primary axis of themulti-layer inductor 120. In this implementation, the key (or theindividual key location 132 within the tactile layer 130) can similarlyinclude a second magnet 152: embedded or overmolded within the key (orkey location 132); defining a second (i.e., opposite) magnetic polarityfacing the multi-layer inductor 120; and extending along a second sideof the primary axis adjacent and opposite the first magnet 151.

In particular, the first magnet 151 can be arranged immediately adjacentthe second magnet 152. The first and second magnets 151, 152 can bearranged directly over the multi-layer inductor 120 and can face themulti-layer inductor 120 with opposing polarities. When the controller170 drives the multi-layer inductor 120 with an alternating voltage (orcurrent), the multi-layer inductor 120 can generate a magnetic fieldthat extends vertically through the substrate 110 and interacts with theopposing magnetic fields of the first and second magnets 151, 152. Morespecifically, when the controller 170 drives the multi-layer inductor120 to a positive voltage during a haptic feedback cycle, themulti-layer inductor 120 can generate a magnetic field that extendsvertically through the substrate 110 in a first vertical direction,which: attracts the first magnet 151 (arranged with the first polarityfacing the multi-layer inductor 120); repels the second magnet 152(arranged with the second polarity facing the multi-layer inductor 120);yields a first lateral force on the key in a first lateral direction;and shifts the key laterally in the first lateral direction relative tothe substrate 110. When the controller 170 then reverses the voltageacross the multi-layer inductor 120 during this haptic feedback cycle,the multi-layer inductor 120 can generate a magnetic field that extendsvertically through the substrate 110 in the opposing vertical direction,which: repels the first magnet 151; attracts the second magnet 152;yields a second lateral force on the key in a second, opposite lateraldirection; and shifts the key laterally in the second lateral directionrelative to the substrate 110.

Therefore, by oscillating the polarity of the multi-layer inductor 120at a key location 132, the controller 170 can: induce oscillatinginteractions (i.e., alternating attractive and repellingforces)—parallel to the substrate 110—between the multi-layer inductor120 and the magnetic element 150 within the adjacent key; and thusoscillate the key (or the key location 132 of the tactile layer 130)horizontally over the substrate 110.

In this implementation, the spiral traces of a single-core multi-layerinductor 120 at a key location 132 can define: a first length (e.g., 0.4inches) along the primary axis of the multi-layer inductor 120; and afirst width (e.g., 0.25 inch, less than first length) along thesecondary axis of the multi-layer inductor 120. Furthermore, the firstmagnet 151 located in the key above this multi-layer inductor 120 candefine: a length parallel to and offset from the primary axis andapproximating the first length of the spiral traces; and a second widthparallel to the secondary axis of the multi-layer inductor 120 andapproximately half of the first width of the spiral traces. The secondmagnet 152 located in the key above this multi-layer inductor 120 cansimilarly define: a length parallel to and offset from the primary axisand approximating the first length of the spiral traces; and a widthparallel to the secondary axis of the multi-layer inductor 120 andapproximately half of the first width of the spiral traces. The firstand second magnets 151, 152 within this magnetic element 150 can beabutted and arranged on each side of the primary axis of the multi-layerinductor 120.

For example, this magnetic element 150 can include a permanent dipolemagnet arranged in the corresponding key and centered over itscorresponding multi-layer inductor 120 such that the two poles of themagnets within this magnetic element 150 are located on opposite sidesof the primary axis of the multi-layer inductor 120. As described above,this magnetic element 150 can also include a set of permanent dipolemagnets arranged in an antipolar configuration (e.g., a Halbach array).

The controller 170 (or the driver) can therefore polarize a multi-layerinductor 120 under a key location 132 by applying an alternating voltageacross the first and second terminals of the multi-layer inductor 120,thereby inducing an alternating current through the set of spiraltraces, inducing an alternating magnetic field normal to the touchsensor surface, inducing oscillating magnetic coupling between themulti-layer inductor 120 and the magnetic element 150 in the key (ortactile layer 130 above), and thus vibrating the key (or a locationregion of the tactile layer 130) in a plane parallel to the substrate110 during a haptic feedback cycle.

10.6 Horizontal Oscillation: Dual-Core Multi-Layer Inductor

Similarly, in the implementation described above in which the substrate110 includes two adjacent single-core, multi-layer inductors 120connected in series at each key location 132, each key (or key location132 within the tactile layer 130) can include: a first magnet 151defining a first magnetic polarity facing its corresponding firstsingle-core multi-layer inductor 120 below and extending along a firstside of a first primary axis of the first single-core multi-layerinductor 120; a second magnet 152 defining a second magnetic polarityfacing the first single-core multi-layer inductor 120 and extendingalong a second side of the first primary axis adjacent the first magnet151; a third magnet defining the second magnetic polarity facing thesecond single-core multi-layer inductor 120 and extending along a firstside of a second primary axis of the second single-core multi-layerinductor 120; and a fourth magnet defining the first magnetic polarityfacing the second single-core multi-layer inductor 120 and extendingalong a second side of the second primary axis adjacent the thirdmagnet.

Accordingly, by oscillating the polarity of the first and secondsingle-core multi-layer inductors 120—which include traces that spiralin the same direction and are therefore in-phase—the controller 170 can:induce oscillating interactions parallel to the substrate 110 betweenthe first single-core multi-layer inductor 120, the first magnet 151,and the second magnet 152 and between the second single-core multi-layerinductor 120, the third magnet, and the fourth magnet; and thusoscillate the key horizontally.

10.7 Vertical Oscillation

In another implementation, each key (or key location 132 within thetactile layer 130) includes a magnetic element 150 arranged relative toits corresponding multi-layer inductor 120 such that the multi-layerinductor 120 at this key location 132 induces an oscillating force onthe magnetic element 150 normal to the substrate 110 and thereforeoscillates the key (or the key location 132 within the tactile layer130) vertically relative to the substrate 110 during a haptic feedbackcycle, as shown in FIG. 10 .

In the implementation described above in which the substrate 110includes a single-core multi-layer inductor 120, each key can include afirst magnet 151: defining a first magnetic polarity facing thesingle-core multi-layer inductor 120; approximately centered over themulti-layer inductor 120; and extending laterally across the primaryaxis of the multi-layer inductor 120. The first magnet 151 can thusgenerate a magnetic field that extends predominantly vertically towardthe multi-layer inductor 120 and that is approximately centered over themulti-layer inductor 120. More specifically, the first magnet 151 cangenerate a magnetic field that extends predominately normal to thesubstrate 110 proximal the center of the multi-layer inductor 120. Asshown in FIG. 10 , when the controller 170 drives the multi-layerinductor 120 to a positive voltage during a haptic feedback cycle, themulti-layer inductor 120 can generate a magnetic field that extendsvertically through the substrate 110 in a first vertical direction,which: repels the first magnet 151 (arranged with the first polarityfacing the multi-layer inductor 120); yields a first vertical force in afirst vertical direction on the first magnetic element 150; and liftsthe corresponding key (or key location 132 within the tactile layer 130)vertically off of the substrate 110. When the controller 170 thenreverses the voltage across the multi-layer inductor 120 during thishaptic feedback cycle, the multi-layer inductor 120 can generate amagnetic field that extends vertically through the substrate 110 in asecond, opposite vertical direction, which: attracts the first magnet151; yields a second vertical force in a second, opposite verticaldirection on the first magnet 151; and draws the corresponding key (orkey location 132 within eh tactile layer 130) downward and back towardthe substrate 110.

Therefore, by oscillating the polarity of a multi-layer inductor 120during a haptic feedback cycle, the controller 170 can: induceoscillating interactions (i.e., alternating attractive and repellingforces)—normal to the substrate 110—between the multi-layer inductor 120and the corresponding magnetic element 150; and thus verticallyoscillate the key (or key location 132 within the tactile layer 130)containing the magnetic element 150.

10.8 Vertical Oscillation: Dual-Core Multi-Layer Inductor

Similarly, in the implementation described above in which the substrate110 includes two adjacent single-core, multi-layer inductors 120connected in series and in phase (i.e., phased by 0°) at each keylocation 132, each key can include a first magnet 151: defining a firstmagnetic polarity facing the first single-core multi-layer inductor 120;approximately centered over the first single-core multi-layer inductor120; and extending laterally across the primary axis of the firstsingle-core multi-layer inductor 120. The key can similarly include asecond magnet 152: defining the first magnetic polarity facing thesecond single-core multi-layer inductor 120; approximately centered overthe second single-core multi-layer inductor 120; and extending laterallyacross the primary axis of the second single-core multi-layer inductor120.

Accordingly, by oscillating the polarity of the first and secondsingle-core multi-layer inductors 120—which are in-phase—at a keylocation 132, the controller 170 can: induce oscillating interactionsnormal to the substrate 110 between the first single-core multi-layerinductor 120 and the first magnet 151 and between the second single-coremulti-layer inductor 120 and the second magnet 152 at this key location132; and thus vertically oscillate the corresponding key (or this keylocation 132 in the tactile layer 130).

11. Variation: Inverted Force Sensing

In one variation, the substrate 110 and force-sensitive layer 160 of thekeyboard system 100 described above are inverted such that: the array ofmulti-layer inductors 120 are arranged across the upper layers of thesubstrate 110; the set of keys are arranged over the top layer 115 ofthe substrate 110; the array of drive electrode and sense electrodepairs 112 are arranged across the bottom layer(s) of the substrate 110;(an electrical shield (e.g., an actively-shielded ground electrode 119)is integrated across a conductive layer of the substrate 110 between thearray of multi-layer inductors 120 and the array of drive electrode andsense electrode pairs 112); and the force-sensitive layer 160 isarranged across the bottom surface of the substrate 110 opposite thekeys. In this variation, the keyboard system 100 can be arranged over arigid planar surface within a chassis of a device, and the substrate 110can communicate a force—applied to a particular key—downward to compressan adjacent region of the force-sensitive layer 160 between thesubstrate 110 and the chassis, thereby locally altering a bulkresistance of the force-sensitive layer 160 below this applied force,which the controller 170 can detect at a cluster of drive electrode andsense electrode pairs 112 and interpret as an input at a particular keyarranged over this cluster of drive electrode and sense electrode pairs112.

12. Variation: Capacitive Sensing

In one variation shown in FIGS. 5 and 6 , the keyboard system 100includes: a substrate 110; a tactile layer 130; an array of magneticelements 150; and a controller 170. In this variation, the substrate 110includes: an array of electrodes 112; and an array of inductors 120arranged below the array of electrodes 112. The tactile layer 130: isarranged over the substrate 110; and defines an array of key locations132 over the array of sense electrodes and the array of inductors 120.Each magnetic element 150 in the array of magnetic elements 150 is:arranged within the tactile layer 130 at a key location 132 in the arrayof key locations 132; and configured to inductively couple to anadjacent inductor 120 in the array of inductors 120. The controller 170is configured to read electrical values from the array of electrodes112. The controller 170 is further configured to, at a first time and inresponse to detecting a change in capacitance value at a first senseelectrode, in the array of electrodes 112: register a first keystroke ofa first key type associated with a first key location 132, in the arrayof key locations 132, defined over the first sense electrode; and drivean oscillating voltage across a first inductor 120, arranged below thefirst sense electrode, during a first haptic feedback cycle to a) inducealternating magnetic coupling between the first inductor 120 and a firstmagnetic element 150, in the array of magnetic elements 150, arrangedwithin the tactile layer 130 below the first key location 132 and b)oscillate the tactile layer 130, at the first key location 132, relativeto the substrate 110.

12.1 Applications: Capacitive Sensing

In this variation, the substrate 110 can include an individual senseelectrode (i.e., in a self-capacitance configuration) or a driveelectrode and sense electrode pair 112 (i.e., in a mutual capacitanceconfiguration) below each key location 132 of the tactile layer 130.Depression of a key location 132 on the tactile layer 130 can thus movethe adjacent magnetic element 150 downward toward the correspondingsense electrode on the substrate 110, thereby effecting the capacitanceof this sense electrode, which the controller 170 can read and interpretas a keystroke at this key location 132. Additionally or alternatively,presence of a finger, stylus, or other object directly over this keylocation 132 may (further) effect the capacitance of this senseelectrode. More specifically, the controller 170 can: read a capacitancevalue (e.g., charge time, discharge time, peak voltage, capacitance)from this sense electrode; detect depression or selection of this keylocation 132 if a difference between this capacitance value and abaseline capacitance value stored for the sense electrode exceeds athreshold difference; and thus register a keystroke of a key typeassociated with this key. Upon detecting depression of the key andregistering this keystroke, the controller 170 can drive an oscillatingvoltage across the same inductor 120, which generates an oscillatingmagnetic field that interacts with and oscillates the same magneticelement 150—and therefore the key. The user may then perceive thisoscillation of the key as downward movement of the key (e.g., analogousto a mechanical snapdome) or otherwise as haptic feedback indicatingthat the controller 170 registered a keystroke at the key.

Therefore, in this variation, a magnetic element 150 at a particular keylocation 132 can function to both: effect capacitance of an adjacentsense electrode on the substrate, which the controller 170 can interpretas a keystroke on the corresponding key; and to magnetically couple tothe adjacent inductor 120 when the controller 170 drives the inductor120 with an oscillating voltage, thereby vibrating the surface of thetactile layer 130 at this key location 132.

12.2 Mutual Capacitance

In this variation, the substrate 110 can include: an array of electrodes112; and an array of inductors 120, each paired with (e.g., arrangedaround or below) an electrode in the array.

In one implementation shown in FIGS. 5 and 6 , in a mutual-capacitanceconfiguration, the keyboard system 100 includes: a drive electrode andsense electrode pair 112 arranged across the top layer 115 of thesubstrate at each key location 132; trace connections between the driveelectrode and sense electrode pairs 112 and the controller 170 acrossrunning across the first and/or second layers of the substrate; a groundelectrode 119 arranged across a third layer 118 of the substrate; and amulti-layer inductor 120 spanning bottom layers of the substrate110—below the third layer 118—below each key location 132.

In this implementation, the tactile layer 130 can include an elasticsublayer 134 (e.g., a compressible silicone or urethane layer):interposed between the substrate 110 and the array of magnetic elements150; and configured to locally compress to enable movement of a firstmagnetic element 150 in a first key location 132 of the tactile layer130 toward a first drive electrode and sense electrode pair 112—on thetop layer 115 of the substrate 110—responsive to application of forceover the first key location 132 on the tactile layer 130, which effects(i.e., changes) capacitance between the first drive electrode and senseelectrode pair 112. The controller 170 can thus: read this change incapacitance from the first sense electrode; interpret this change incapacitance as a keystroke on the first key location 132 (e.g., if thiscapacitance differs from a stored baseline capacitance by more than athreshold difference); and drive an alternating voltage across the firstmulti-layer inductor 120, which generates an oscillating magnetic fieldthat a) extends through the upper layers of the substrate 110 and theelastic sublayer 134 and b) oscillates the first magnetic element 150and the first key location 132 during a first haptic feedback cycle.Similarly, the elastic sublayer 134 of the tactile layer 130 can locallycompress to enable movement of a second magnetic element 150 in a secondkey location 132 of the tactile layer 130 toward a second driveelectrode and sense electrode pair 112—on the top layer 115 of thesubstrate 110—responsive to application of force over the second keylocation 132 on the tactile layer 130, which effects capacitance betweenthe second drive electrode and sense electrode pair 112. The controller170 can thus: read this change in capacitance from the second senseelectrode; interpret this change in capacitance as a keystroke on thesecond key location 132; and drive an alternating voltage across thesecond multi-layer inductor 120 in order to oscillate the secondmagnetic element 150 and the second key location 132 during a secondhaptic feedback cycle.

Alternatively, in this configuration, the keyboard system 100 caninclude: a multi-layer inductor 120 spanning the top and upper layers ofthe substrate 110 at each key location 132; and a drive electrode andsense electrode pair 112 arranged across the top layer 115 of thesubstrate around (e.g., circumscribing) a multi-layer inductor 120 ateach key location 132. In this implementation, the first key location132 of the tactile layer 130 can compress to enable the first magneticelement 150 to move toward the first multi-layer inductor 120 when thefirst key location 132 is depressed. The first magnetic element 150 canthus effect capacitance between the first drive electrode and senseelectrode pair 112, which the controller 170 can read from the firstsense electrode and interpret as a keystroke at the first key location132. Accordingly, the controller 170 can drive an alternating voltageacross the first multi-layer inductor 120 to oscillate the firstmagnetic element 150 and the first key location 132 during a hapticfeedback cycle responsive to detecting this keystroke.

Additionally or alternatively, in this configuration, a finger incontact with a key location 132 on the tactile layer 130 can effect thecapacitance of the drive electrode and sense electrode pair 112 underthe corresponding key location 132, and the controller 170 can interpreta keystroke at this key location 132 and execute a haptic feedback cycleat this multi-layer inductor 120 accordingly.

However, in this variation, the set of keys and/or the tactile layer 130can define any other form of discrete or continuous keys, such asdescribed above, and the controller 170 can implement similar methodsand techniques to detect keystrokes at these key locations 132.

12.3 Self Capacitance

Alternatively, in a self-capacitance configuration, the keyboard system100 includes: a sense electrode arranged on the top layer 115 of thesubstrate at each key location 132; a ground electrode 119 arrangedacross a second layer 117 of the substrate; and a multi-layer inductor120 spanning bottom layers of the substrate 110—below the second layer117—below each key location 132.

In a similar implementation, the keyboard system 100 includes: amulti-layer inductor 120 spanning the top and upper layers of thesubstrate 110 below each key location 132; and a sense electrodearranged on the top layer 115 of the substrate around a multi-layerinductor 120 at each key location 132. Thus, in this implementation, asense electrode can be particularly sensitive to detecting a finger onthe key location 132 of the tactile layer 130 overhead the senseelectrode, and the multi-layer inductor 120 adjacent this senseelectrode can be nearest to and exhibit greatest capacitive coupling tothe magnetic element 150 at this location.

In a similar implementation, the keyboard system 100 includes: amulti-layer inductor 120 spanning the top and upper layers of thesubstrate 110 below each key location 132; and a sense electrodearranged on the top layer 115 of the substrate and located proximal thecenter of a multi-layer inductor 120 at each key location 132. Thus, inthis implementation, a sense electrode can be particularly sensitive todetecting motion of the magnetic element 150 toward the substrate whenthe tactile layer 130 overhead the sense electrode is depressed.

In this configuration, a sense electrode at a key location 132 cancapacitively couple to the magnetic element 150 above. Therefore,depression of the tactile layer 130 at this key location 132 can movethis magnetic element 150 toward the multi-layer inductor 120, therebyeffecting the capacitance of this sense electrode. The controller 170can interpret the resulting change in capacitance of the sense electrodeas a keystroke at this key location 132 and execute a haptic feedbackcycle at this multi-layer inductor 120 accordingly.

Additionally or alternatively, a sense electrode at a key location 132can capacitively couple to a finger in contact with or depressing thecorresponding key location 132 on the tactile surface above. Therefore,presence of a finger on the tactile layer 130 at this key location 132depression can effect the capacitance of this sense electrode. Thecontroller 170 can interpret the resulting change in capacitance of thesense electrode as a keystroke at this key location 132 and execute ahaptic feedback cycle at this multi-layer inductor 120 accordingly.

Alternatively, magnetic elements in the key elements can be connected toa reference potential or to ground. Accordingly, a sense electrode at akey location 132 can capacitively couple to the magnetic element in thekey element above. Therefore, depression of the key element (e.g., by afinger on the tactile layer 130 at this key location 132) can move themagnetic element toward the sense electrode effect the capacitance ofthis sense electrode. The controller 170 can interpret the resultingchange in capacitance of the sense electrode as a keystroke at this keylocation 132 and execute a haptic feedback cycle at this multi-layerinductor 120 accordingly.

Yet alternatively, the system 100 can include a conductive film or layerarranged above or below these magnetic elements, arranged above thearray of sense electrodes, and connected to a reference potential or toground. Accordingly, a sense electrode at a key location 132 cancapacitively couple to this conductive film. Therefore, depression ofthe key element (e.g., by a finger on the tactile layer 130 at this keylocation 132) can locally move the conductive film toward the senseelectrode and effect the capacitance of this sense electrode. Thecontroller 170 can interpret the resulting change in capacitance of thesense electrode as a keystroke at this key location 132 and execute ahaptic feedback cycle at this multi-layer inductor 120 accordingly.

However, in this variation, the keyboard system can include an array ofelectrodes 112 arranged in any other configuration.

12.4 Controller

Therefore, in this variation, the controller 170 can: read electricalvalues in the form of capacitance values from the array of electrodes112; and register a first keystroke of a first key type in response to acapacitance value—read from a first sense electrode under a first keylocation 132 on the tactile layer 130—differing from a stored baselinecapacitance value for the first sense electrode by more than a firstthreshold capacitance value, the first threshold capacitance valuecorresponding to a minimum keystroke force.

In one implementation described above, a first magnetic element 150 at afirst key location 132 in the tactile layer 130 affects capacitance of afirst sense electrode in the substrate 110 responsive to movement of thefirst magnetic element 150 toward a first multi-layer inductor 120 underthis first key location 132. Similarly, a second magnetic element 150 ata second key location 132 in the tactile layer 130 affects capacitanceof a second electrode in the substrate 110 responsive to movement of thesecond magnetic element 150 toward a second multi-layer inductor 120under this second key location 132.

Accordingly, in response to detecting a first change in electrical value(e.g., in a first direction, such as increase in charge time, decreasein peak voltage, increase in capacitance, decrease in circuit frequency)at a first sense electrode at a first key location 132, the controller170 can: register a first keystroke of a first key type associated withthe first key location 132; and drive an oscillating voltage across afirst inductor 120 under the first key location 132 during a firsthaptic feedback cycle to a) induce alternating magnetic coupling betweenthe first inductor 120 and a first magnetic element 150 arranged withinthe tactile layer 130 at the first key location 132 and b) oscillate thetactile layer 130, at the first key location 132, relative to thesubstrate 110, thereby communicating haptic feedback into a user'sfinger or stylus to indicate that the controller 170 registered thefirst keystroke. However, because the tactile layer 130 (e.g., theelastic sublayer 134) is elastic, the tactile layer 130 can return thefirst magnetic element 150 back to its nominal condition as the force onthe first key location 132 is removed, thereby returning the capacitanceof the first sense electrode to (or near) its baseline capacitance.Therefore, in response to detecting a second change in electrical value(e.g., in a second direction, such as decrease in charge time, increasein peak voltage, decrease in capacitance, increase in circuit frequency)at the first sense electrode, the controller 170 can: register releaseof the first key location 132; and drive an oscillating voltage (e.g.,at a higher frequency, over a shorter duration, and/or at a loweramplitude) across the first inductor 120 during a second haptic feedbackcycle to a) induce alternating magnetic coupling between the firstinductor 120 and the first magnetic element 150 and b) oscillate thetactile layer 130, at the first key location 132, relative to thesubstrate 110, thereby communicating haptic feedback into the user'sfinger or stylus to indicate that the controller 170 detected release ofthe first key location 132.

Similarly, in response to detecting a third change in electrical value(e.g., in the first direction) at the second inductor 120, thecontroller 170 can: register a second keystroke of a second key typeassociated with the second key location 132 defined over the secondmulti-layer inductor 120; and drive the oscillating voltage across thesecond inductor 120 during a third haptic feedback cycle to a) inducealternating magnetic coupling between the second inductor 120 and thesecond magnetic element 150 arranged within the tactile layer 130 at thesecond key location 132 and b) oscillate the tactile layer 130, at thesecond key location 132, relative to the substrate 110. Furthermore, inresponse to detecting a fourth change in electrical value (e.g., in thesecond direction) at the first sense electrode, the controller 170 can:register release of the second key location 132; and drive anoscillating voltage (e.g., at the higher frequency, over the shorterduration, and/or at the lower amplitude) across the second inductor 120during a fourth haptic feedback cycle to a) induce alternating magneticcoupling between the second inductor 120 and the second magnetic element150 and b) oscillate the tactile layer 130, at the second key location132, relative to the substrate 110, thereby communicating hapticfeedback into the user's finger or stylus to indicate that thecontroller 170 detected release of the second key location 132.

13. Variation: Inductive Sensing

In one variation shown in FIGS. 7-10 , the keyboard system 100 includes:a substrate 110; a tactile layer 130; an array of magnetic elements 150;and a controller 170. The substrate 110 includes an array of inductors120. The tactile layer 130: is arranged over the substrate 110; anddefines an array of key locations 132 over the array of inductors 120.Each magnetic element 150 in the array of magnetic elements 150: isarranged within the tactile layer 130 at a key location 132 in the arrayof key locations 132; is configured to inductively couple to an adjacentinductor 120 in the array of inductors 120; and is configured to moverelative to the adjacent inductor 120 responsive to application of aforce on the tactile layer 130 at the key location 132. The controller170 is configured to read electrical values from the array of inductors120. The controller 170 is further configured to, at a first time and inresponse to detecting a first change in electrical value at a firstinductor 120, in the array of inductors 120: register a first keystrokeof a first key type associated with a first key location 132, in thearray of key locations 132, defined over the first inductor 120; anddrive an oscillating voltage across the first inductor 120 during afirst haptic feedback cycle to a) induce alternating magnetic couplingbetween the first inductor 120 and a first magnetic element 150, in thearray of magnetic elements 150, arranged within the tactile layer 130 atthe first key location 132 and b) oscillate the tactile layer 130, atthe first key location 132, relative to the substrate 110.

In this variation, the controller 170 can further, at a second time andin response to detecting a second change in electrical value at a secondinductor 120, in the array of inductors 120: register a second keystrokeof a second key type associated with a second key location 132 definedover the second inductor 120; and drive the oscillating voltage acrossthe second inductor 120 during a second haptic feedback cycle to a)induce alternating magnetic coupling between the second inductor 120 andthe second magnetic element 150 arranged within the tactile layer 130 atthe second key location 132 and b) oscillate the tactile layer 130, atthe second key location 132, relative to the substrate 110.

13.1 Applications: Inductive Sensing

Generally, in this variation, rather than detect depression of a keybased on a change in resistance or capacitance across electrodes at keylocations 132 on the substrate 110, magnetic elements 150 in the keyscan inductively (or “magnetically”) couple to their adjacent inductors120. When a user depresses an individual key in the keyboard, themagnetic element 150 within the key moves toward its correspondinginductor 120, thereby changing a magnetic field and magnetic fluxthrough the inductor 120, inducing a voltage in a first direction acrossthe inductor 120, and/or causing current to flow in a first directionthrough the inductor 120. In this variation, the controller 170 can reada magnitude of this voltage and/or current moving through the inductor120. The controller 170 can thus detect depression of the key andregister a keystroke of the corresponding key type: if the magnitude ofthis voltage exceeds a threshold voltage; if the integral of themagnitude of this voltage over a time interval (e.g., 50 milliseconds)exceeds a threshold keystroke value; or if the current moving throughthe inductor 120 within a time interval exceeds a thresholdcurrent—which may indicate depression of the key with sufficient forceover a limited time interval characteristic of depression of amechanical switch, button, or snapdome. Upon detecting depression of thekey and registering a keystroke of the corresponding key type, thecontroller 170 can drive an oscillating voltage across the same inductor120, which generates an oscillating magnetic field that interacts withand oscillates the same magnetic element 150—and therefore the key. Theuser may then perceive this oscillation of the key as downward movementof the key (e.g., analogous to a mechanical snapdome) or otherwise ashaptic feedback indicating that the controller 170 registered akeystroke at the key.

Therefore, in this variation, the keyboard system 100 can omit senseelectrodes and/or drive electrode at each key location 132 and/or aforce-sensitive layer 160, as described above. Rather, the keyboardsystem 100 can include a single inductor 120 and magnetic element 150pair at each key location 132. The controller 170 can both: detect aninput on an individual key of the keyboard based on changes in voltageacross or current through the inductor 120 below this individual key;and return haptic feedback at the individual key by driving anoscillating voltage across this particular inductor 120. Morespecifically, in this variation, the single inductor 120 and the singlemagnetic element 150 located at each key location 132 can function both:as a sensor configured to detect inputs on the corresponding key; and asa haptic actuator configured to return vibratory feedback to a finger orother object depressing the key.

13.2 Tactile Layer

Generally, the tactile layer 130 is arranged over the substrate 110 anddefines an array of key locations 132 over the array of inductors 120integrated into the substrate 110.

13.2.1 Contiguous Elastic Layer with Embedded Magnetic Elements

In one implementation described above and shown in FIGS. 7 and 8 , thetactile layer 130 includes an elastic sublayer 134 that defines aunitary structure and forms a contiguous surface spanning the array ofkey locations 132. In this implementation, each magnetic element 150—inthe array of magnetic elements 150 integrated into the tactile layer130—can include a single magnet or a magnetic array (e.g., a Halbacharray) embedded or overmolded in the elastic sublayer 134 below a keylocation 132 in the array of key locations 132 defined across thetactile layer 130.

For example, the tactile layer 130 can be assembled by: injectionmolding or casting a bottom silicone or urethane layer that includes ashallow recess or counterbore at each key location 132; locating apreformed magnetic element 150 in each recess or counterbore on thefirst layer 116; molding a top silicone or urethane layer definingconcave or convex ridges around each key location 132; and the bondingor vulcanizing a top layer 115 onto the bottom layer to enclose themagnetic elements 150.

In another example, the tactile layer 130 can be assembled by: locatingmagnetic elements 150 at key locations 132 within a mold; and thenshooting a polymer (e.g., silicone, urethane) into the mold toencapsulate the magnetic elements 150 and complete the tactile layer130.

Therefore, in this implementation, application of a force on the tactilelayer 130 at a key location 132 can compress a region of the elasticsublayer 134 below this force and thus move a magnetic element 150 atthis key location 132 toward the multi-layer inductor 120 such that themagnetic element 150 induces current flow through a multi-layer inductor120 below the magnetic element 150. The controller 170 can detect thiscurrent flow through this multi-layer inductor 120 as a keystroke atthis key location 132.

13.2.2 Contiguous Elastic Sublayer Below Key Elements

In another implementation shown in FIGS. 5 and 6 , the tactile layer 130includes: an elastic sublayer 134 arranged over the substrate 110; a setof discrete rigid key elements 140 arranged over and coupled (e.g.,bonded) to the elastic sublayer 134 at key locations 132; and a set ofmagnetic elements 150 integrated into discrete keys or into the elasticsublayer 134 at the key locations 132.

For example, in this implementation, each discrete rigid key element 140can: be coupled to a discrete region of the elastic sublayer 134 over amulti-layer inductor 120 integrated into the substrate 110; define a keylocation 132; and house a magnetic element 150. In this example,responsive to application of a force on the discrete rigid key element140, the discrete rigid key can compress this discrete region of theelastic sublayer 134 and thus move the magnetic element 150 toward themulti-layer inductor 120 such that the magnetic element 150 inducescurrent flow through the multi-layer inductor 120 under this keylocation 132. The controller 170 can detect this current flow throughthis multi-layer inductor 120 as a keystroke at this key location 132.

In particular, in this variation, the tactile layer 130 can include anelastic sublayer 134 (or layer, material): interposed between thesubstrate 110 and the array of magnetic elements 150; configured tolocally compress to enable movement of a first magnetic element 150toward a first inductor 120 responsive to application of force over afirst key location 132 on the tactile layer 130; configured to locallycompress to enable movement of a second magnetic element 150 toward asecond inductor 120 responsive to application of force over a second keylocation 132 on the tactile layer 130; etc. The first magnetic element150 inductively couples to the first inductor 120 and induces currentflow in a first direction through the first inductor 120 as the firstmagnetic element 150 moves downward from its nominal position toward thefirst inductor 120 during depression of the first key location 132.However, the elastic sublayer 134 is configured to elastically deformand to return the first magnetic element 150 to its nominal positionwhen a force on the first key location 132 of the tactile layer 130 isreleased. Accordingly, the first magnetic element 150 can induce currentflow in a second, opposite direction through the first inductor 120 asthe first magnetic element 150 moves away from the first inductor 120and back toward its nominal position when a force on the first keylocation 132 is released.

Similarly, the second magnetic element 150 inductively couples to thesecond inductor 120 and induces current flow in the first directionthrough the second inductor 120 as the second magnetic element 150 movesdownward from its nominal position toward the second inductor 120 duringdepression of the second key location 132. The second magnetic element150 also induces current flow in the second, opposite direction throughthe second inductor 120 as the second magnetic element 150 moves awayfrom the second inductor 120 and back toward its nominal position when aforce on the second key location 132 is released.

13.2.3 Discrete Keys with Retention Posts

In another implementation shown in FIGS. 1 and 2 , the keyboard system100 includes multiple discrete keys that cooperate to form the tactilelayer 130, wherein each discrete key defines a retention post 142installed through a bore at a corresponding key location 132 in thesubstrate 110.

For example, in this implementation, the substrate 110 can define anarray of bores adjacent the array of inductors 120, such as centeredinside and passing through the cores of these inductors 120. In thisexample, the keyboard system 100 can include a set of discrete keyelements 140 arranged over the substrate and cooperating to form thetactile layer 130. Each discrete key element 140: defines a key face;includes an elastic post extending rearward from the key face; isinstalled over an inductor 120 with its elastic post a) extendingthrough a bore in the substrate 110 and b) retaining the discrete keyelement 140 over the substrate 110; and houses a magnetic element 150.

Furthermore, responsive to application of a force on its key face, adiscrete key element 140 can compress against the substrate and move themagnetic element 150—located within the discrete key element 140—towardthe adjacent inductor 120 at this key location 132 such that themagnetic element 150 induces current flow through the inductor 120 in afirst direction. The controller 170 can: detect this current flowthrough this inductor 120 in the first direction (or detect a voltageacross the inductor 120 at a first polarity) as a keystroke at this keylocation 132; and execute a haptic feedback cycle (e.g., a “keystroke”haptic feedback cycle) at this inductor 120 to tactilely indicatedetection of a keystroke at this key location 132.

Similarly, responsive to release of the force from the key face, thisdiscrete key element 140 can rebound (or “spring back”) to move themagnetic element 150 away from the adjacent inductor 120 and back towardits nominal position over the inductor 120 such that the magneticelement 150 induces current flow through the inductor 120 in a second,opposite direction. The controller 170 can: detect this current flowthrough this inductor 120 in the second direction (or detect a voltageacross the inductor 120 at a second, opposite polarity) as release ofthis key location 132; and execute a haptic feedback cycle (e.g., a“release” haptic feedback cycle at a higher frequency, at a loweramplitude, and/or over a shorter duration) at this inductor 120 totactilely indicate detection of release of this key location 132 andcompletion of the keystroke.

13.3 Substrate and Inductors: In-Plane/Horizontal Oscillation

As described above, the substrate 110 can define a unitary structureincluding: a first layer 116 that includes a first array of spiraltraces; and a second layer 117 arranged below the first layer 116opposite the tactile layer 130 and that includes a second array ofspiral traces. Each spiral trace in the first layer 116 can be locatedbelow a key location 132 on the tactile layer 130, can be coiled in afirst direction, and can define a first end and a second end. Eachspiral trace in the second layer 117: can be located below a keylocation 132 in the array of key locations 132; can be coiled in asecond direction opposite the first direction; can define a third endand a fourth end, the third end electrically coupled to a second end ofa first spiral trace in the first array of spiral traces; and cancooperate with the adjacent spiral trace to form a first loop—of aninductor 120 arranged below a key location 132—that defines a primaryaxis.

In this implementation and as described above, a first magnetic element150 located at a first key location 132 in the tactile layer 130includes: a first magnet 151 arranged over the first inductor 120 on afirst side of a primary axis of the first inductor 120 and defining afirst polarity facing the first inductor 120; and a second magnet 152adjacent the first magnet 151, arranged over the first inductor 120 on asecond side of a primary axis of the first inductor 120 opposite thefirst magnet 151, and defining the first polarity facing away from thefirst inductor 120.

Then, in response to detecting a keystroke at the first key location 132on the tactile layer 130, the controller 170 can drive an oscillatingvoltage across the first inductor 120 during a haptic feedback cycle to:induce alternating magnetic coupling between the first inductor 120, thefirst magnet 151, and the second magnet 152; and oscillate the tactilelayer 130—at the first key location 132 containing the first and secondmagnets 151, 152—parallel to the substrate 110 (i.e., horizontally), asshown in FIG. 9 .

13.4 Normal/Vertical Oscillation

In another implement described above, the substrate 110 can define aunitary structure including: a first layer 116 that includes a firstarray of spiral traces and a third array of spiral traces; and a secondlayer 117 arranged below the first layer 116 opposite the tactile layer130 and that includes a second array of spiral traces and a fourth arrayof spiral traces. Each spiral trace in the first array of spiral tracesin the first layer 116 can be located below a key location 132 on thetactile layer 130, can be coiled in a first direction, and can define afirst end and a second end. Each spiral trace in the second array ofspiral traces in the second layer 117: can be located below a keylocation 132 in the array of key locations 132; can be coiled in asecond direction opposite the first direction; can define a third endand a fourth end, the third end electrically coupled to a second end ofa first spiral trace in the first array of spiral traces; and cancooperate with the adjacent spiral trace to form a first loop—of aninductor 120 arranged below a key location 132—that defines a primaryaxis. Each spiral trace in the third array of spiral traces in the firstlayer 116: can be adjacent a first spiral trace in the first array ofspiral traces; can be coiled in the second direction; and can define afifth end and a sixth end, the fifth end electrically coupled to thefirst end of the first spiral trace.

Similarly, in this implementation, each spiral trace in the fourth arrayof spiral traces in the second layer 117: can be adjacent a secondspiral trace in the second array of spiral traces; can be coiled in thefirst direction; can define a seventh end and an eighth end, the seventhend electrically coupled to a sixth end of a third spiral trace in thethird array of spiral traces; can cooperate with a first spiral trace inthe first array of spiral traces, the second spiral trace, and the thirdspiral trace to form an inductor 120 below a key location 132 on thetactile layer 130; and can cooperate with the third spiral trace to forma second loop of the inductor 120 such that the second loop of theinductor 120 defines a secondary axis parallel to and offset from aprimary axis of a first loop of the inductor 120.

Furthermore, in this implementation, a first magnetic element 150 at afirst key location 132 can include: a first magnet 151 arranged over aprimary axis of a first loop of the first inductor 120 and defining afirst polarity facing a first inductor 120 in the substrate 110; and asecond magnet 152 adjacent the first magnet 151, arranged over asecondary axis of a second loop of the first inductor 120, and definingthe first polarity facing away from the first inductor 120.

Then, in response to detecting a keystroke at the first key location 132on the tactile layer 130, the controller 170 can drive a oscillatingvoltage across the first inductor 120 during the first haptic feedbackcycle to: induce alternating magnetic coupling between the first magnet151 and the first loop of the first inductor 120; induce alternatingmagnetic coupling between the second magnet 152 and the second loop ofthe first inductor 120; and oscillate the tactile layer 130—at the firstkey location 132—normal to the substrate 110 (i.e., vertically), asshown in FIG. 10 .

13.5 Controller

Generally, the controller 170 is configured to: read electrical values(e.g., current directions and amplitudes; voltage polarities andamplitudes) from the array of inductors 120; register keystrokes atparticular key locations 132 on the tactile layer 130 responsive tochanges in electrical values at inductors 120 (e.g., from baseline“null” current amplitudes) under these key locations 132; and to driveoscillating voltages across these inductors 120 during haptic feedbackcycles responsive to detecting keystrokes at these key locations 132.

13.5.1 Keystroke Detection

In this variation, the tactile layer 130 can include an elastic sublayer134 (or layer, material): interposed between the substrate 110 and thearray of magnetic elements 150; configured to locally compress to enablemovement of each magnetic elements 150 at a key location 132 toward itscorresponding inductor 120 responsive to application of a force overthis key location 132 on the tactile layer 130; and configured torebound (or “spring back”) to return each magnetic element 150 to itsnominal position over its corresponding inductor 120 when a force isreleased from this key location 132 on the tactile layer 130. Movementof a magnetic element 150 toward its corresponding inductor 120—when aforce is applied to the tactile layer 130 at the corresponding keylocation 132 (e.g., with a finger or stylus)—induces inductive couplingbetween the magnetic element 150 and the inductor 120 and causes currentto flow in a first direction through the inductor 120 and thus generatesa voltage of a first polarity across the inductor 120.

As shown in FIGS. 9 and 10 , the controller 170 can: detect this currentflow and direction through the inductor 120 (e.g., via an ammeterconnected to the controller 170 and/or detect this voltage and voltagepolarity across the inductor 120 (e.g., via an integrated or connectedanalog-to-digital converter) when the corresponding key location 132 isdepressed; and register a keystroke—of a key type associated with thiskey location 132 and inductor 120—such as if the total current throughthe inductor 120, the total current through the inductor 120 within athreshold time interval (e.g., 1 millisecond), the peak voltage acrossthe inductor 120, or the integral of voltages across the inductor 120over the time interval aligns with a first current direction or firstvoltage polarity and exceeds a threshold keystroke value. Uponregistering this keystroke at this key location 132, the controller 170can: output a key type associated with this key location 132 (e.g., to aconnected device or processor); set an “active keystroke” flag for thiskey location 132; and output an oscillating voltage to the inductor 120,which inductively couples to the adjacent magnetic element 150 andvibrates the tactile layer 130 at this key location 132, as describedabove.

13.5.2 Release Detection

As described above and shown in FIG. 9 , the tactile layer 130 isconfigured to elastically deform and to return magnetic elements 150 totheir nominal position when force on the tactile layer 130 atcorresponding key locations 132 are released. Accordingly, each magneticelement 150 can induce current flow in a second, opposite directionthrough an adjacent inductor 120 as the tactile layer 130 moves themagnetic element 150 away from this inductor 120 and back toward itsnominal position when a force on the corresponding key location 132 isreleased.

For example, the tactile layer 130 can include an elastic sublayer 134(or layer, material): interposed between the substrate 110 and the arrayof magnetic elements 150; configured to locally compress to enablemovement of a magnetic element 150—at a key location 132 on the tactilelayer 130—toward its corresponding inductor 120 responsive toapplication of a force over this key location 132; and configured torebound (or “spring back”) to return each magnetic element 150 to itsnominal position over its corresponding inductor 120 when a force isreleased from this key location 132 on the tactile layer 130. Movementof a magnetic element 150 away from its corresponding inductor 120—whena force previously applied to the tactile layer 130 at the correspondingkey location 132 (e.g., with a finger or stylus) is released—inducesinductive coupling between the magnetic element 150 and the inductor 120and causes current to flow in a second, opposite direction through theinductor 120 and thus generates a voltage of a second polarity acrossthe inductor 120.

The controller 170 can: detect this current flow and direction throughthe inductor 120 and/or detect this voltage and voltage polarity acrossthe inductor 120 when the corresponding key location 132 is released;and then register a key release event and/or completion of a keystroke,such as if the total current through the inductor 120, the total currentthrough the inductor 120 within a threshold time interval (e.g., 1millisecond), the peak voltage across the inductor 120, or the integralof voltages across the inductor 120 over the time interval aligns with asecond current direction or second voltage polarity and exceeds athreshold key release value (e.g., less than the threshold keystrokevalue described above). Upon registering this keystroke release at thiskey location 132, the controller 170 can: clear an active keystroke flagfor this key location 132; and output an oscillating voltage to theinductor 120 (e.g., at a higher frequency, over a shorter duration,and/or at a lower amplitude than a keystroke haptic feedback cycle whena keystroke at this key location 132 was last detected), whichinductively couples to the adjacent magnetic element 150 and vibratesthe tactile layer 130 at this key location 132, as described above, totactilely indicate to a user that the controller 170 detected andregistered release of this key location 132.

13.5.3 Examples

For example, in this variation, the controller 170 can: read electricalvalues from the array of inductors 120 by tracking voltage across thearray of inductors 120; detect a first voltage of a first polarityacross a first inductor 120 at a first time (e.g., during a first scancycle); register a first keystroke of a first key type associated withthe first inductor 120 in response to detecting the first voltage of thefirst polarity across the first inductor 120; and drive an oscillatingvoltage across the first inductor 120 during a first haptic feedbackcycle in response to registering the first keystroke. Later, thecontroller 170 can: detect a second voltage of a secondpolarity—opposite the first polarity—across the first inductor 120 at asecond time succeeding the first time (e.g., during a second scan cyclesucceeding the first scan cycle); register release of the firstkeystroke from the first key location 132 on the tactile layer 130 inresponse to detecting the second voltage at the second polarity acrossthe first inductor 120; and drive a second oscillating voltage acrossthe first inductor 120 during a second haptic feedback cycle in responseto registering release of the first keystroke from the first keylocation 132.

Furthermore, in this example, the controller 170 can: register the firstkeystroke of the first key type in response to the first voltageexceeding a first threshold voltage magnitude; drive the oscillatingvoltage across the first inductor 120 at a first frequency during thefirst haptic feedback cycle in response to registering the firstkeystroke; register release of the first keystroke from the first keylocation 132 on the tactile layer 130 in response to the second voltageexceeding a second threshold voltage magnitude less than the firstthreshold voltage magnitude; and drive the second oscillating voltageacross the first inductor 120 at a second frequency greater than thefirst frequency during a second haptic feedback cycle in response toregistering release of the first keystroke from the first key location132.

In another example, the controller 170 can: read electrical values fromthe array of inductors 120 by tracking current flow through the array ofinductors 120; detect a first change in electrical value including afirst current moving through the first inductor 120 in a first directionat a first time (e.g., during a first scan cycle); register the firstkeystroke of the first key type in response to detecting the firstcurrent moving through the first inductor 120 in the first direction;and drive the oscillating voltage across the first inductor 120 during afirst haptic feedback cycle in response to registering the firstkeystroke. Later, the controller 170 can: detect a second current movingthrough the first inductor 120 in a second direction opposite the firstdirection at a second time succeeding the first time (e.g., during asecond scan cycle); register release of the first keystroke from thefirst key location 132 on the tactile layer 130 in response to detectingthe second current moving through the first inductor 120 in the seconddirection; and drive a second oscillating voltage across the firstinductor 120 during a second haptic feedback cycle in response toregistering release of the first keystroke from the first key location132.

In this example, the controller 170 can also: register the firstkeystroke of the first key type in response to the first current, movingthrough the first inductor 120 in the first direction, exceeding a firstthreshold current amplitude; drive the oscillating voltage across thefirst inductor 120 at a first frequency during the first haptic feedbackcycle in response to registering the first keystroke; register releaseof the first keystroke from the first key location 132 on the tactilelayer 130 in response to the second current, moving through the firstinductor 120 in the second direction, exceeding a second thresholdcurrent amplitude less than the first threshold current amplitude; anddrive the second oscillating voltage across the first inductor 120 at asecond frequency greater than the first frequency during a second hapticfeedback cycle in response to registering release of the first keystrokefrom the first key location 132.

13.5.4 Inductor Sampling

In one implementation shown in FIG. 11 , the array of inductors 120 isconnected to a set of row and column traces, and the controller 170 canbe coupled to the array of inductors 120 via a coil driver 171 and theserow and column traces. Accordingly, the controller 170 can selectivelyexecute a haptic feedback cycles at a particular inductor 120 bytriggering the coil driver 171 to drive oscillating voltages across aparticular combination of one row trace and one column trace uniquelyconnected to this particular inductor 120. In this implementation, thecontroller 170 (or other reader connected to these row and columntraces) can also serially read currents through and/or voltages acrossindividual inductors 120 during a scan cycle and detect keystrokes andkey releases from individual key locations 132 on the tactile layer 130during this scan cycle based on these currents and/or voltages. Forexample, during a scan cycle, the controller 170 can: read a firstvoltage across a first row trace and a first column trace correspondingto a first inductor 120 in the substrate 110; read a second voltageacross the first row trace and a second column trace corresponding to asecond inductor 120 in the substrate 110; read a third voltage acrossthe first row trace and a third column trace corresponding to a thirdinductor 120 in the substrate 110; and repeat this process for eachother row and column trace combination to read voltages at each inductor120 during this scan cycle.

The controller 170 can then: detect selection of the first key location132 on the tactile layer 130 during this scan cycle if the first voltageexhibits a first polarity (e.g., is positive) and is greater than athreshold voltage; register a new keystroke at the first key location132 and set an “active keystroke” flag for the first key location 132 ifan active keystroke flag is not currently set for the first key location132; and trigger the coil driver 171 to execute a keystroke hapticfeedback cycle at the first inductor 120. Similarly, the controller 170can: detect selection of the second key location 132 on the tactilelayer 130 during this scan cycle if the second voltage exhibits thefirst polarity and is greater than the threshold voltage; but discardthis selection at the second key location 132 if an active keystrokeflag is currently set for the second key location 132. (The controller170 can also clear the active keystroke flag for the second key location132 after a threshold duration of time (e.g., 700 milliseconds) afterthis active keystroke flag was last set for the second key location132.) Additionally or alternatively, the controller 170 can: detectrelease of the third key location 132 on the tactile layer 130 duringthis scan cycle if the second voltage exhibits a second, oppositepolarity and is greater than the threshold voltage; clear the “activekeystroke” flag for the third key location 132 if an active keystrokeflag is currently set for the third key location 132; and trigger thecoil driver 171 to execute a release haptic feedback cycle at the thirdinductor 120. The controller 170 can repeat this process for each otherkey location 132 and voltage read during this scan cycle.

The controller 170 can then repeat this process for each subsequent scancycle, such as at a rate of 20 Hz.

Furthermore, in the foregoing implementation, while executing a hapticfeedback cycle (e.g., a keystroke or release haptic feedback cycle) at aparticular inductor 120, the controller 170 can selectively sample onlyrow and column traces not connected to the particular inductor 120. Inparticular, because the particular inductor 120 may inducehigh-amplitude noise through the row and column traces connected theretoduring a haptic feedback cycle, the controller 170 can selectivelysample only row and column traces not connected to the particularinductor 120 during subsequent scan cycles until the coil driver 171completes the haptic feedback cycle at the particular inductor 120, atwhich time the controller 170 can resume scanning the row and columntraces connected to the particular inductor 120.

Conversely, the controller 170 (or other reader) and the coil driver 171can be directly and selectively coupled to each inductor 120, such asvia a multiplexer and a demultiplexer, respectively. For example, thecoil driver 171 can selectively execute a haptic feedback cycle at aparticular inductor 120 by selectively addressing the particularinductor 120 via a demultiplexer. As the coil driver 171 executes thishaptic feedback cycle at the particular inductor 120, the controller 170can: serially select and then read voltages across or currents througheach other inductor 120 in the keyboard system 100; interpret keystrokesand/or keystroke releases on key locations 132 over these otherinductors 120; and selectively trigger the coil driver 171 to executesubsequent haptic feedback cycles at these other inductors 120accordingly. Once the coil driver 171 completes the haptic feedbackcycle at the particular inductor 120, the controller 170 can resumereading read voltages across or currents through the particular inductor120 and each other inductor 120 in the keyboard system 100 not currentlyundergoing a haptic feedback cycle.

13.6 Illumination

As described above, in this variation, the keyboard system 100 canfurther include a set of light elements 180 configured to illuminate (or“backlight”) key locations 132 across the tactile layer 130 or discretekey elements 140.

In one example shown in FIGS. 5 and 6 , the tactile layer 130 includesan array of translucent regions 144 arranged within the array of keylocations 132, such as translucent elastomeric or rigid elements in theform of alphanumeric and keyboard characters cast or molded into thetactile layer 130 at each key location 132 and extending through thethickness of the tactile layer 130. In this example, each inductor 120can define a spiral trace: fabricated on a first layer 116 of thesubstrate 110 facing the tactile layer 130; and facing a key location132 of the tactile layer 130. The keyboard system 100 further includesan array of light elements 180. Each light element 180: is arranged onthe top layer 115 of the substrate 110 adjacent (e.g., centered withinor located adjacent a perimeter of) a spiral trace of an inductor 120 ata key location 132; faces the tactile layer 130; and is configured toilluminate a translucent region 144 within the adjacent key location 132of the tactile layer 130. In this example, the back layer of the tactilelayer 130 can include recesses to accommodate these light elements 180,and the translucent elements within the tactile layer 130 can bearranged directly over these light elements 180.

As shown in FIG. 9 , the tactile layer 130 can include a network oflight pipes 182 extending laterally across the tactile layer 130 andvertically to the surface of the tactile layer 130 at each key location.The system 100 can also include a light element 180 arranged on the toplayer of the substrate and facing an input end of the network of lightpipes. Thus, the system 100 can activate the light element 180 toilluminate the network of light pipes 182, which funnels light to thesurfaces of and illuminates the key locations.

However, the keyboard system 100 can include a set of light elements 180arranged in any other configuration and configured to directly orindirectly illuminate key locations 132 or discrete key elements 140 inany other way.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the embodiments of the invention without departing fromthe scope of this invention as defined in the following claims.

I claim:
 1. A keyboard system comprising: a substrate comprising anarray of inductors; a tactile layer: arranged over the substrate; anddefining an array of key locations over the array of inductors; an arrayof magnetic elements, each magnetic element in the array of magneticelements: arranged within the tactile layer at a key location in thearray of key locations; configured to inductively couple to an adjacentinductor in the array of inductors; and configured to move relative tothe adjacent inductor responsive to application of a force on thetactile layer at the key location; and a controller configured to: readelectrical values from the array of inductors; and at a first time, inresponse to detecting a first change in electrical value at a firstinductor, in the array of inductors: register a first keystroke of afirst key type associated with a first key location, in the array of keylocations, defined over the first inductor; and drive an oscillatingvoltage across the first inductor during a first haptic feedback cycleto: induce alternating magnetic coupling between the first inductor anda first magnetic element, in the array of magnetic elements, arrangedwithin the tactile layer at the first key location; and oscillate thetactile layer, at the first key location, relative to the substrate. 2.The keyboard system of claim 1, wherein the controller is furtherconfigured to read a second set of electrical values from the array ofinductors at a send time succeeding the first time; and in response todetecting a second change in electrical value at a second inductor, inthe array of inductors, in the second set of electrical values: registera second keystroke of a second key type different from the first keytype and associated with a second key location, in the array of keylocations, defined over the second inductor; and drive the oscillatingvoltage across the second inductor during a second haptic feedback cycleto: induce alternating magnetic coupling between the second inductor anda second magnetic element, in the array of magnetic elements, arrangedwithin the tactile layer at the second key location; and oscillate thetactile layer, at the second key location, relative to the substrate. 3.The keyboard system of claim 2, wherein the controller is configured to:read the second set of electrical values, from a subset of inductors inthe array of inductors and excluding the first inductor, during thefirst haptic feedback cycle; and initiate the second haptic feedbackcycle at the second inductor prior to completion of the first hapticfeedback cycle.
 4. The keyboard system of claim 1, wherein thecontroller is configured to: read electrical values from the array ofinductors by tracking voltage across the array of inductors; detect thefirst change in electrical value comprising a first voltage of a firstpolarity across the first inductor at the first time; register the firstkeystroke of the first key type in response to detecting the firstvoltage of the first polarity across the first inductor; drive theoscillating voltage across the first inductor during the first hapticfeedback cycle in response to registering the first keystroke; detect asecond voltage of a second polarity, opposite the first polarity, acrossthe first inductor at a second time succeeding the first time; registerrelease of the first keystroke from the first key location on thetactile layer in response to detecting the second voltage at the secondpolarity across the first inductor; and drive a second oscillatingvoltage across the first inductor during a second haptic feedback cyclein response to registering release of the first keystroke from the firstkey location.
 5. The keyboard system of claim 4, wherein the controlleris configured to: register the first keystroke of the first key type inresponse to the first voltage exceeding a first threshold voltagemagnitude; drive the oscillating voltage across the first inductor at afirst frequency during the first haptic feedback cycle in response toregistering the first keystroke; register release of the first keystrokefrom the first key location on the tactile layer in response to thesecond voltage exceeding a second threshold voltage magnitude less thanthe first threshold voltage magnitude; and drive the second oscillatingvoltage across the first inductor at a second frequency greater than thefirst frequency during a second haptic feedback cycle in response toregistering release of the first keystroke from the first key location.6. The keyboard system of claim 1, wherein the controller is configuredto: read electrical values from the array of inductors by trackingcurrent flow through the array of inductors; detect the first change inelectrical value comprising a first current moving through the firstinductor in a first direction at the first time; register the firstkeystroke of the first key type in response to detecting the firstcurrent moving through the first inductor in the first direction; drivethe oscillating voltage across the first inductor during the firsthaptic feedback cycle in response to registering the first keystroke;detect a second current moving through the first inductor in a seconddirection opposite the first direction at a second time succeeding thefirst time; register release of the first keystroke from the first keylocation on the tactile layer in response to detecting the secondcurrent moving through the first inductor in the second direction; anddrive a second oscillating voltage across the first inductor during asecond haptic feedback cycle in response to registering release of thefirst keystroke from the first key location.
 7. The keyboard system ofclaim 1: wherein the tactile layer comprises an elastic sublayer:interposed between the substrate and the array of magnetic elements;configured to locally compress to enable movement of the first magneticelement toward the first inductor responsive to application of forceover the first key location on the tactile layer; and configured tolocally compress to enable movement of a second magnetic element, in thearray of magnetic elements, toward a second inductor, in the array ofinductors, responsive to application of force over a second keylocation, in the array of key locations, on the tactile layer; whereinthe first magnetic element inductively couples to the first inductor andinduces current flow in a first direction through the first inductorresponsive to movement toward the first inductor; wherein the secondmagnetic element inductively couples to the second inductor and inducescurrent flow in the first direction through the second inductorresponsive to movement toward the second inductor; and wherein thecontroller is further configured to, at a second time, in response todetecting a second change in electrical value at the second inductor:register a second keystroke of a second key type associated with thesecond key location defined over the second inductor; and drive theoscillating voltage across the second inductor during a second hapticfeedback cycle to: induce alternating magnetic coupling between thesecond inductor and the second magnetic element arranged within thetactile layer at the second key location; and oscillate the tactilelayer, at the second key location, relative to the substrate.
 8. Thekeyboard system of claim 1: wherein the tactile layer comprises anelastic sublayer: defining a unitary structure; and forming a contiguoussurface spanning the array of key locations; and wherein each magneticelement in the array of magnetic elements comprises a magnet overmoldedin the elastic sublayer below a key location in the array of keylocations.
 9. The keyboard system of claim 1: wherein the tactile layercomprises an elastic sublayer arranged over the substrate and a set ofdiscrete rigid key elements; and wherein each discrete rigid keyelement, in the set of discrete rigid key elements: is coupled to adiscrete region of the elastic sublayer over an inductor in the array ofinductors; defines a key location in the array of key locations; housesa magnetic element in the array of magnetic elements; and is configuredto compress the discrete region of the elastic sublayer and to move themagnetic element toward the inductor responsive to application of aforce on the discrete rigid key element, the magnetic element inducingcurrent flow through the inductor responsive to motion toward theinductor.
 10. The keyboard system of claim 1: wherein the substratedefines an array of bores adjacent the array of inductors; wherein thetactile layer comprises a set of discrete key elements arranged over thesubstrate and cooperating to form the tactile layer; and wherein eachdiscrete key element, in the set of discrete key elements: defines a keyface; comprises an elastic post extending rearward from the key face; isinstalled over an inductor, in the array of inductors, with the elasticpost: extending through a bore, in the array of bores, in the substrate;and retaining the discrete key element over the substrate houses amagnetic element in the array of magnetic elements; and is configured tocompress against the substrate and to move the magnetic element towardthe inductor responsive to application of a force on the key face, themagnetic element inducing current flow through the inductor responsiveto motion toward the inductor.
 11. The keyboard system of claim 1,wherein the substrate defines a unitary structure comprising: a firstlayer comprising a first array of spiral traces, each spiral trace inthe first array of spiral traces: located below a key location in thearray of key locations; coiled in a first direction; and defining afirst end and a second end; and a second layer arranged below the firstlayer opposite the tactile layer and comprising a second array of spiraltraces, each spiral trace in the second array of spiral traces: locatedbelow a key location in the array of key locations; coiled in a seconddirection opposite the first direction; defining a third end and afourth end, the third end electrically coupled to a second end of afirst spiral trace in the first array of spiral traces; and cooperatingwith the adjacent spiral trace to form a first loop: of an inductor, inthe array of inductors, below a key location, in the array of keylocations; and defining a primary axis.
 12. The keyboard system of claim11: wherein the first magnetic element comprises: a first magnet:arranged over the first inductor on a first side of a primary axis ofthe first inductor; and defining a first polarity facing the firstinductor; and a second magnet: adjacent the first magnet; arranged overthe first inductor on a second side of a primary axis of the firstinductor opposite the first magnet; and defining the first polarityfacing away from the first inductor; and wherein the controller isconfigured to drive the oscillating voltage across the first inductorduring the first haptic feedback cycle to: induce alternating magneticcoupling between the first inductor, the first magnetic, and the secondmagnet; and oscillate the tactile layer, at the first key location,parallel to the substrate.
 13. The keyboard system of claim 11: whereinthe first layer of the substrate further comprises a third array ofspiral traces, each spiral trace in the third array of spiral traces:adjacent a first spiral trace in the first array of spiral traces;coiled in the second direction; and defining a fifth end and a sixthend, the fifth end electrically coupled to the first end of the firstspiral trace; wherein the second layer of the substrate furthercomprises a fourth array of spiral traces, each spiral trace in thefourth array of spiral traces: adjacent a second spiral trace in thesecond array of spiral traces; coiled in the first direction; defining aseventh end and an eighth end, the seventh end electrically coupled to asixth end of a third spiral trace in the third array of spiral traces;cooperating with a first spiral trace in the first array of spiraltraces, the second spiral trace, and the third spiral trace to form aninductor, in the array of inductors, below a key location in the arrayof key locations; and cooperating with the third spiral trace to form asecond loop of the inductor, the second loop of the inductor defining asecondary axis parallel to and offset from a primary axis of a firstloop of the inductor; wherein the first magnetic element comprises: afirst magnet: arranged over a primary axis of a first loop of the firstinductor; and defining a first polarity facing the first inductor; and asecond magnet: adjacent the first magnet; arranged over a secondary axisof a second loop of the first inductor; and defining the first polarityfacing away from the first inductor; and wherein the controller isconfigured to drive the oscillating voltage across the first inductorduring the first haptic feedback cycle to: induce alternating magneticcoupling between the first magnet and the first loop of the firstinductor; induce alternating magnetic coupling between the second magnetand the second loop of the first inductor; and oscillate the tactilelayer, at the first key location, normal to the substrate.
 14. Thekeyboard system of claim 1: wherein the tactile layer comprises an arrayof translucent regions arranged within the array of key locations;wherein each inductor, in the array of inductors, defines a spiraltrace: fabricated on a first layer of the substrate facing the tactilelayer; and facing a key location in the array of key locations; andfurther comprising an array of light elements, each light element in thearray of light elements: arranged on the first layer of the substrateadjacent a spiral trace of an inductor in the array of inductors; facinga key location, in the array of key locations, of the tactile layer; andconfigured to illuminate a translucent region within the key location.15. A keyboard system comprising: a substrate comprising: an array ofelectrodes; and an array of inductors, each inductor in the array ofinductors paired with an electrode in the array of electrodes; a tactilelayer: arranged over the substrate; and defining an array of keylocations over the array of inductors; a force-sensitive layerinterposed between the tactile layer and the substrate and exhibitingvariations in local contact resistance across the array of electrodesresponsive to variations in force applied to the tactile layer at thearray of key locations; an array of magnetic elements, each magneticelement in the array of magnetic elements: arranged within the tactilelayer at a key location in the array of key locations; and configured toinductively couple to an adjacent inductor in the array of inductors;and a controller configured to: read electrical values from the array ofelectrodes; and at a first time, in response to detecting a change inelectrical value at a first sense electrode, in the array of electrodes:register a first keystroke of a first key type associated with a firstkey location, in the array of key locations, defined over the firstsense electrode; and drive an oscillating voltage across a firstinductor, arranged below, the first sense electrode, during a firsthaptic feedback cycle to: induce alternating magnetic coupling betweenthe first inductor and a first magnetic element, in the array ofmagnetic elements, arranged within the tactile layer at the first keylocation; and oscillate the tactile layer, at the first key location,relative to the substrate.
 16. The keyboard system of claim 15: whereinthe array of electrodes comprises a drive electrode and sense electrodepair arranged on the substrate below each key location in the array ofkey locations; wherein the force-sensitive layer bridges gaps betweendrive electrode and sense electrode pairs in the array of electrodes;and wherein the controller is configured to: read electrical values fromthe array of electrodes by: driving drive electrodes in the array ofelectrodes with a reference voltage; and reading sense voltages fromsense electrodes in the array of electrodes; and register the firstkeystroke in response to a first sense voltage, read from the firstsense electrode, differing from a stored baseline voltage for the firstsense electrode by more than a first threshold voltage, the firstthreshold voltage corresponding to a minimum keystroke force.
 17. Thekeyboard system of claim 16, wherein the controller is configured to: atsecond time succeeding the first time, read a second set of electricalvalues from the array of electrodes; and register release of the firstkeystroke from the first key location in response to a second sensevoltage, read from the first sense electrode at the second time,differing from the stored baseline voltage for the first sense electrodeby less than a second threshold voltage, the second threshold voltageless than the first threshold voltage.
 18. A keyboard system comprising:a substrate comprising: an array of electrodes; and an array ofinductors arranged below the array of electrodes; a tactile layer:arranged over the substrate; and defining an array of key locations overthe array of sense electrode and the array of inductors; an array ofmagnetic elements, each magnetic element in the array of magneticelements: arranged within the tactile layer at a key location in thearray of key locations; and configured to inductively couple to anadjacent inductor in the array of inductors; and a controller configuredto: read electrical values from the array of electrodes; and at a firsttime, in response to detecting a change in capacitance value at a firstsense electrode, in the array of electrodes: register a first keystrokeof a first key type associated with a first key location, in the arrayof key locations, defined over the first sense electrode; and drive anoscillating voltage across a first inductor, arranged below, the firstsense electrode, during a first haptic feedback cycle to: inducealternating magnetic coupling between the first inductor and a firstmagnetic element, in the array of magnetic elements, arranged within thetactile layer below the first key location; and oscillate the tactilelayer, at the first key location, relative to the substrate.
 19. Thekeyboard system of claim 18, wherein the controller is configured to:read electrical values in the form of capacitance values from the arrayof electrodes; and register the first keystroke in response to a firstcapacitance value, read from the first sense electrode, differing from astored baseline capacitance value for the first sense electrode by morethan a first threshold capacitance value, the first thresholdcapacitance value corresponding to a minimum keystroke force.
 20. Thekeyboard system of claim 19: wherein the tactile layer comprises anelastic sublayer: interposed between the substrate and the array ofmagnetic elements; configured to locally compress to enable movement ofthe first magnetic element toward the first electrode responsive toapplication of force over the first key location on the tactile layer;and configured to locally compress to enable movement of a secondmagnetic element, in the array of magnetic elements, toward a secondelectrode, in the array of electrode, responsive to application of forceover a second key location, in the array of key locations, on thetactile layer; wherein the first magnetic element affects capacitance ofthe first electrode responsive to movement of the first magnetic elementtoward the first inductor; wherein the second magnetic element affectscapacitance of the second electrode responsive to movement of the secondmagnetic element toward the second inductor; and wherein the controlleris further configured to, at a second time, in response to detecting asecond change in electrical value at the second inductor: register asecond keystroke of a second key type associated with the second keylocation defined over the second inductor; and drive the oscillatingvoltage across the second inductor during a second haptic feedback cycleto: induce alternating magnetic coupling between the second inductor andthe second magnetic element arranged within the tactile layer at thesecond key location; and oscillate the tactile layer, at the second keylocation, relative to the substrate.